Pump chamber and valve assembly

ABSTRACT

A medical infusion pump (10) using a pump chamber cassette (86) has a housing (20,22) defining a pump chamber cassette receptacle (84) and a pump driving mechanism (250) for propelling liquid through the pump chamber cassette. A door (50) holds the pump chamber cassette (86) within the cassette receptacle (84) in an operative position relative to the driving mechanism (250). The cassette includes an elastomeric conduit (132), a frame (134) and clips (146,148) for attaching the elastomeric conduit (132) to the frame (134) for holding the elastomeric conduit (132) in a select position relative to the pump driving mechanism (250) of the infusion pump upon placement of the cassette (86) in an operative position relative to the pump driving mechanism (250). An anti-free flow device (136,138) includes the flexible conduit (132) received between an anvil (182) fixedly attached to the frame (134) and a pincher (132) attached to the frame (134), the pincher (138) being movable between a first position biasing the pincher (138) against the anvil (182) to occlude a lumen (150) of the elastomeric conduit (132) and a second position for eliminating the bias of the pincher (138) against the anvil (182) so as to not occlude the lumen (150) of the elastomeric conduit (132). The elastomeric conduit (132) is made of an elongate elastomeric robe having an inlet valve portion (142) and an outlet valve portion (144) made of a furst material and a chamber portion (140) disposed therebetween, the chamber portion being made of a second material. The first material has a durometer of less than a durometer of the second material. The chamber portion (140), inlet valve portion (142) and the outlet valve portion (144) may have a football-shaped cross-section.

This is a divisional of application Ser. No. 08/209/518 filed on Mar. 9,1994, now U.S. Pat. No. 5,982,446

BACKGROUND OF THE INVENTION

The present invention is directed toward a medical infusion pump and,more particularly, toward an ambulatory infusion pump for accurately andsafely administering a wide range of infusion rates.

BACKGROUND ART

Spiraling health care costs have led to the development of a variety ofdevices for facilitating administration of intravenous therapy topatients outside of a clinical setting. In addition, doctors have foundthat in many instances patients can return to substantially normallives, provided that they can receive continuous intravenousadministration of medication. These factors have combined to promote thedevelopment of lightweight, portable or ambulatory infusion pumps whichcan be worn by a patient and are capable of administering a continuoussupply of medication at a desired rate.

A wide variety of ambulatory pumps in use in the medical field areintended to meet the need of a high degree of accuracy in theadministration of fluids to maximize the effectiveness of medication andto protect the patient. Typically, these ambulatory infusion pumpsinclude a pump control unit and drive mechanism including a variety ofoperating controls adapted to accept a disposable pump chamber assembly.One known pumping mechanism includes inlet and outlet valves and asingle liquid displacement plunger, and will be referred to herein as asingle plunger, two valve pump. Each pumping cycle in this type of pumpbegins with the outlet valve closed and the inlet valve open. Fluidflows from a source container into a section of tubing disposed betweenthe inlet and outlet valve. After this section of tubing has filled withliquid, the inlet valve closes and the outlet valve opens. The plungerthen compresses the short section of tubing between the valves,displacing the liquid contained therein and forcing it through the pump.

Maintaining an accurate flow rate from single plunger, two valve pumpshas proven to be difficult. One significant problem in maintaining anaccurate, consistent flow rate is the requirement that the tubingrecover to a consistent internal diameter upon the plunger releasing thecompression of the tube between the valves to ensure the same volume offluid is delivered in each pump cycle. If the volume of the passagedefining the pumping chamber changes over time, for example, due tochanges in tubing elasticity, the pump's flow rate will also change.Tubing which is commonly used for disposable tube sets in medicalpumping applications is known to experience changes in elasticity overtime with repetitive compression of the tubing, thereby affecting theextent to which the tubing recovers when a compression force is removed.One manner of successfully compensating for changes in elasticity isaltering the pump rate. Another attempt at compensating for changes isdisclosed in Natwick et al., U.S. Pat. No. 5,055,001. Natwick disclosesthe use of shapers adjacent the plunger which bias the tube to return toits undeformed state following compression by the plunger. Such shapers,however, result in a more complex pump mechanism, increase the weight ofthe pump mechanism, and require energy input to operate and aretherefore an unsatisfactory solution to maintaining a consistent pumpchamber volume in an ambulatory infusion pump.

Another problem with single plunger, two valve pumps of the typediscussed above is variations in the volume of the pumping chamber dueto system pressure variances. Natwick et at., U.S. Pat. No. 5,055,001,is directed toward resolving this problem by providing complicated inletand outlet valve structures that each exert a first sealing force which,under application of a cracking pressure, will allow flow of fluidthrough the valves. The cracking pressure therefore becomes a consistentpressure within the pump chamber which is intended to result in auniform pump chamber discharge volume. The valve structure of Natwickrequires numerous parts which increase pump weight and the complexity ofmanufacture.

An additional problem facing known ambulatory pumps using a disposablepump chamber assembly is preventing inadvertent free flow of liquid froma liquid reservoir through the disposable pump chamber assembly duringloading and unloading of the pump chamber assembly. A variety ofanti-free flow devices have been devised to address this problem.However, a need exists for an anti-free flow device formed as part ofthe pump chamber assembly, with the assembly being readily loaded by auser into a pump chamber receptacle of an infusion pump in a positionpreventing free flow of liquids and which is readily changed to aposition allowing flow of liquid by closure of the receiving receptacle.Furthermore, an anti-free flow device which automatically preventsfree-flow during loading and unloading of the disposable pump chamberassembly is desirable.

Known ambulatory infusion pumps are programmable to control the rate atwhich medication is infused to a patient and to vary the profile ofpatient dosages. However, these known ambulatory infusion pumps haveseveral drawbacks. First, the range of delivery rates is too narrow forapplication in a broad range of therapies. This has resulted indevelopment of pumps having pumping rates within a select rangedelivering select therapies. In addition, in order to obtain variable,accurate infusion rates, known ambulatory infusion pumps requirerelatively large amounts of electric power, leading to quick depletionof battery supplies. As a result, either many heavy batteries arerequired to keep the pumps operable for extended periods, or thebatteries must be changed frequently. This results in patient discomfortor inconvenience. Thus, there is a clear need in the field of ambulatoryinfusion pumps for a compact energy efficient ambulatory infusion pumpcapable of delivering medication across a wide range of infusion rateswhile ensuring pump safety.

The present invention is directed to overcoming some of the problemsdiscussed above.

SUMMARY OF THE INVENTION

One aspect of the present invention is a pump chamber cassette for usewith a medical infusion pump. The medical infusion pump has a housingdefining a pump chamber cassette receptacle, the housing furthercontaining a driving mechanism for propelling liquid through the pumpchamber cassette. A cooperating structure between the pump chambercassette and the cassette receptacle maintain the pump chamber cassettein an operative position relative to the driving mechanism. The pumpchamber cassette includes a flexible conduit, a frame and clips forattaching the flexible conduit to the frame for holding the flexibleconduit in a select position relative to the pump driving mechanism ofthe infusion pump upon placement of the cassette in an operativeposition relative to the driving mechanism. An anvil is fixedly attachedto the frame. A pincher is attached to the frame with a space betweenthe pincher and the anvil and a flexible conduit is received in thespace between the pincher and the anvil. A slider on the frame ismovable between a first position biasing the pincher against the anvilto occlude the lumen of the flexible conduit and a second position foreliminating the bias of the pincher against the anvil so as to notocclude the lumen of the flexible conduit.

A second aspect of the present invention is a pump chamber for use witha medical infusion pump as generally described in the precedingparagraph, the infusion pump including a pump driving mechanism havingan inlet pincher valve, an outlet pincher valve and a plungerintermediate the inlet and outlet pincher valves. The pump chamber is anelongate elastomeric tube having an inlet valve portion and an outletvalve portion made of a first material and a chamber portion disposedtherebetween, the chamber portion being made of a second material. Thelumen extends through the inlet and outlet valve portions and thechamber portion. The first material has a durometer less than thedurometer of the second material. The inlet valve portion, the outletvalve portion and the chamber portion are spaced relative to one anotherso that with the pump chamber in an operative position within the pumpchamber receptacle, the inlet valve portion is proximate the inletpincher valve, the chamber portion is proximate the plunger, and theoutlet valve potion is proximate to the outlet pincher valve. In anexemplary embodiment, the inlet and outlet valve portions are made ofpolyvinylchloride having an outer diameter of about 0.163 inches and aninner diameter of about 0.083 inches with a durometer of between 30 and60 shore A and the pump chamber is made of polyurethane tubing having aninner diameter of about 0.157 inches, an outer diameter of about 0.193inches and a durometer of about 80 shore A.

Another aspect of the present invention is an improved pump chambercassette for use in a peristaltic infusion pump of the type describedabove. The improved pump chamber cassette includes an elastomeric tubehaving a football shaped cross-section and a rigid frame. Theelastomeric tube is attached to the rigid frame by clips which, with thecassette received in an operative position within the cassettereceptacle, maintain the elastomeric tube between the valve pinchers andthe platen with the minor axis of the football shaped cross-sectionaligned parallel to the direction of movement between the valve pinchersand a platen.

Another aspect of the present invention is a medical infusion pump forintravenous delivery of medical liquids to a patient comprising a pumpchamber assembly including a pump chamber having a lumen therethroughand an anti-free flow device movable between an occluding position foroccluding the lumen to prevent liquid flow through the pump chamber anda non-occluding position for not occluding the lumen to allow liquidflow through the pump chamber. A housing includes a receptacle forreceiving the pump chamber assembly. A door on the housing is pivotablebetween a first position confining the pump chamber assembly within thereceptacle in an operative position and a second position not confiningthe pump chamber assembly within the receptacle. A pumping apparatuswithin the housing is operatively associated with the receptacle forpropelling liquid through the pump chamber assembly when the pumpchamber assembly is received within the receptacle in an operativeposition. The pumping mechanism propels liquid through the pump chamberassembly by sequentially occluding select portions of the pump chamberlumen. A latch on the door is operatively associated with the anti-freeflow device and the door for moving the anti-free flow device betweenthe occluding position and the non-occluding position as an incident ofthe door first being moved to the first position and for moving theconfining means from the first position after the anti-free flow deviceis moved to the occluding position.

The pump chamber cassette of the present invention is readily loadedinto a cassette receptacle of an infusion pump with little risk ofinadvertent free flow during loading and unloading of the cassette fromthe pump. The cassette also cooperates with the cassette receptacle toproperly align the cassette and pump chamber with the pump drivingmechanism. The pump chamber/valve assembly of the pump chamber cassetteprovides a pump chamber designed to optimize repeatability of the pumpchamber volume, as well as speed and reliability of the pump chamberrebound so as to provide accurate, repetitive pump discharges. The valveportion of the pump chamber assembly minimizes the energy required toocclude the lumen of the valve portion, thereby minimizing energyconsumption during pump operation. The inlet and outlet valve portionshaving a football shaped cross-section further minimize energy requiredto occlude the inlet and outlet valve portions. Together, these featuresfacilitate a highly reliable, accurate infusion pump while minimizingthe complexity of the pumping apparatus, the weight of the pumpingapparatus and the energy required to operate the pumping apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a patient wearing an ambulatory infusionpump of the present invention;

FIG. 2 is a perspective view of the ambulatory infusion pump with thefront cover slid to an open position;

FIG. 3 is a perspective view of the back of the ambulatory infusion pumpwith a solution bag in fluid communication with a pump cassette loadedinto the ambulatory infusion pump;

FIG. 4 is an exploded perspective view of the pump cassette receptacleof the ambulatory infusion pump;

FIG. 5 is a perspective view of the pump cassette receptacle and a pumpcassette illustrating loading of the pump cassette into the pumpcassette receptacle;

FIG. 6 is a partial plan view of the pump cassette received in the pumpcassette receptacle of the present invention with a latch in a "closed"position and a cassette receptacle cover cut-away except by the latch;

FIG. 7 differs from FIG. 6 only in that the latch is in an position;

FIG. 8A is an exploded perspective view of the pump cassette;

FIG. 8B is a perspective view of a clip for attaching the pump chamberassembly to the rigid frame;

FIG. 8C is a section view of the pump chamber assembly and clip takenalong line 8C--8C of FIG. 5;

FIG. 8D is a section view of the pump chamber assembly and clip takenalong line 8D--8D of FIG. 5;

FIG. 9 is a section view of the inlet valve tube taken along line 9--9of FIG. 8 including the platen and inlet pincher valve;

FIG. 10 is a section view of the inlet valve tube of FIG. 9 in acompressed state;

FIG. 11A is a perspective view of an alternative embodiment of the inletvalve tube;

FIG. 11B is a section view of the alternative embodiment of the inletvalve tube taken along line 11B--11B of FIG. 11A including the platenand inlet pincher valve;

FIG. 12 is a section view of the slider stop of the pump cassette;

FIG. 13 is a sectional view of a latch detent of the present inventiontaken along line 13--13 of FIG. 6;

FIG. 14 is an exploded sectional perspective view illustratinginteraction of the sliding latch, latch detent and spike.

FIG. 15 is a perspective view of a pump driving mechanism of the presentinvention with a portion of a plunger motor removed for clarity;

FIG. 16 is an exploded perspective view of the pump driving mechanism;

FIG. 17 is a perspective view of the inlet and outlet rocker arms of thepump driving mechanism;

FIG. 18A-18D are left side views with respect to FIG. 17 of the inletvalve cam and the outlet valve cam in engagement with the crank carrierconnected to the valve motor shaft;

FIG. 19 is a right side view with respect to FIG. 16 of the plunger camand plunger;

FIG. 20 is an exploded perspective view of a position encoder/magneticdetent of the plunger motor;

FIG. 21 is a sectional view of the transducer button wedge bearing uponthe pump chamber;

FIG. 22 is a perspective view of the ambulatory infusion pump receivedin a soft pump case with the case open;

FIG. 23 is a perspective view of the ambulatory infusion pump mounted inthe soft pump case with the patient display exposed;

FIG. 24 is a perspective view of the rear of the soft pump case;

FIG. 25 is a plan view of the control panel and beveled front surface ofthe ambulatory infusion pump;

FIG. 26 is a plan view of the patient display;

FIG. 27 is a plan view of the program main display with a "selectdelivery" mode screen;

FIG. 28 is a plan view of the programming display with a sample "setup"screen;

FIG. 29 is a plan view of the programming display with a sample "mode"screen;

FIG. 30 is a plan view of the programming display with a sample "pumphistory" screen;

FIGS. 31A-D are sectional views illustrating the pumping action of thepump valves and plunger on the pump chamber/valve assembly;

FIG. 32 is a block diagram of an electrical circuit for the ambulatoryinfusion pump;

FIG. 33 is an electrical schematic for a watchdog circuit of theambulatory infusion pump;

FIG. 34 is a block diagram of an electrical circuit for the remoteprogrammer;

FIG. 35A is a flow diagram of the main routine of the monitormicroprocessor software for use with the ambulatory infusion pump;

FIG. 35B is a flow diagram of the "support patient display and patientcontrols" subroutine of FIG. 35A;

FIG. 35C is a flow diagram of the "support communication with controlmicroprocessor" subroutine of FIG. 35A;

FIG. 35D is a flow diagram of the "support communication with the remoteprogrammer" subroutine of FIG. 35A;

FIG. 36A is a flow diagram of the main routine of the controlmicroprocessor software;

FIG. 36B is a flow diagram of the mode "1" delivery routine;

FIG. 36C is a flow diagram of the mode "2" delivery routine;

FIG. 36D is a flow diagram of the mode "3" delivery routine;

FIG. 36E is a flow diagram of the mode "4" delivery routine;

FIG. 36F is a flow diagram of the mode "5" delivery routine;

FIG. 36G is a flow diagram of the "fill and valve leak test" sequence ofFIG. 36A;

FIG. 36H is a flow diagram of the "sleep" routine;

FIG. 36I-36L are a series of flow diagrams of the "fault recoveryattempt" routine;

FIGS. 37A-E illustrate the five pump delivery profiles;

FIG. 38 is a table summarizing pump operation during the five fluiddelivery modes;

FIG. 39 is a schematic representation of the pump peripheralscommunicatingly associated;

FIG. 40 is a plan view of the remote programmer unit;

FIG. 41 is a block diagram of an electrical circuit for a remotecommunication interface unit for use with the ambulatory infusion pump;

FIG. 42 is a graph of DMA tan Δ of a variety of pump tubing materials;and

FIG. 43 is a graph of DMA stiffness of a variety of pump tubingmaterials.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates an ambulatory infusion pump (10) contained within asoft pump case (12) mounted to an ambulatory patient (14). Theambulatory infusion pump (10) is designed to provide a wide variety ofdrug delivery profiles so that a wide variety of therapies can beadministered by the ambulatory infusion pump. The compact size and lightweight of the pump facilitate a patient wearing the pump so that acontinuous supply of medication can be delivered to the patient whilethe patient can engage in normal everyday activities. A flexible IV tube(16), which typically is made of PVC, extends between the pump (10) anda needle/catheter (18) for intravenous infusion of medication from thepump to the ambulatory patient. The ambulatory infusion pump (10) isusable in other applications where the distal end of the IV tube isconnected to some other apparatus disposed downstream of the pump (10).

A. Pump Housing

The pump housing is designed for ease of patient and clinician use aswell as patient comfort when the ambulatory pump (10) is worn. FIGS. 2and 3 illustrate the pump housing. The ambulatory infusion pump (10)includes a rigid housing front (20) and a rigid housing back (22) whichare preferably made of a high density rigid polymer such aspolycarbonate and are joined by a continuous tongue and groove interfacearound their peripheries. A front cover (24) is slidably mounted to therigid front housing (20) to selectively cover and uncover a controlpanel (26) on the rigid housing front (20). The control panel (26)includes an LCD programmer display (28) and a keyboard (30). The frontcover (24) therefore protects and conceals the control panel to preventinadvertent actuation of the keyboard (30). Detents (not shown) may beprovided on the front cover (24) to maintain the front cover in aposition coveting or not coveting the control panel (26). The keyboard(30) are membrane switch pants. A user control panel (32) is located ona beveled front surface (34) of the rigid housing front (20). The usercontrol panel (32) includes a patient display (36), a start/stop button(38) and a bolus dose control button (40). An LED (41) is provided onthe user control panel (32) for providing a visual alarm or alert. Alsoon the rigid housing front (20) is a remote bolus switch contact (42) towhich a remote bolus switch (44) can be coupled by means of electricalcontact wire (46) (see FIG. 1). The pump is programmable so that apatient may use the bolus dose control button (40) or the remote bolusswitch (44) to self-administer a bolus of medication, as for example inpatient-controlled analgesic (PCA) therapies. Programming of the pump(10) will be discussed in greater detail below.

The rigid housing back (22) is best illustrated in FIG. 3. A cassettedoor (50) made of a rigid polymer such as glass-filled polycarbonate ispivotably attached to the rigid housing back (22) by a pair of hinges(52,54) (see FIGS. 4 and 5). A latch (56) is slidably mounted to therigid housing back (22) to selectively capture and release the cassettedoor (50) in a manner which will be discussed in detail below. A channel(58) in the rigid housing back (22) cooperates with a hemispherical slot(60) in the cassette door (50) to define a passage for receiving the IVtubing (62) in fluid communication with a fluid supply such as asolution bag (64). As illustrated in FIG. 3, the flexible tubing (62) isbrought into fluid communication with the solution bag (64) by means ofa spike (66) received in the solution bag outlet (68).

As seen in FIG. 3, between the rigid housing front (20) and the rigidhousing back (22) is an infrared or IR window (70) made of molded tintedplastic which allows transmission of an IR signal to and from theambulatory infusion pump (10). A sliding battery door (72) permitsaccess to a cavity (74) which receives a 9 V battery (not shown) toprovide electric power to the ambulatory infusion pump (10). An on/offswitch (76) to power "on" or "off" the ambulatory infusion pump (10) isalso provided. A rear panel (78) on the rigid housing back (22) bears aninstruction label (80) consisting of an adhesive coated polyester. Thepolyester instruction label (80) also functions to cover mechanicalaccess holes in the rigid housing back (22) so as to provide a moisturebarrier.

FIG. 4 and 5 illustrates a portion of the rigid housing back (22)including the cassette door (50) pivoted open about the hinges (52,54)to reveal a pump cassette receptacle (84) for receiving a pump cassette(86) in a manner discussed below. As seen in FIG. 4, the cassette door(50) has a pair of hinge knuckles (88) laterally spaced from oneanother. The hinge knuckles (88) are received between a pair of hingeknuckles (90) on the rigid housing back (22). A pair of hinge pins (92)are received within lengthwise holes in the hinge knuckles (88,90) topivotably secure the cassette door (50) to the rigid housing back (22).

The cassette door (50) defines an inner recess (94) which contains afloating platen assembly (96). The floating platen assembly (96)consists of a rigid metal platen (98) which is biased away from thecassette door (50) by a plurality of leaf springs (100) in lengthwiseside-by-side relation. The leaf springs (100) are received between alateral leaf spring bracket (102) and a pair of longitudinal leaf springbrackets (104) integrally formed with and extending from the door (50)which selectively restrain the leaf springs (100) from lateral orlengthwise movement relative to the cassette door (50). In the preferredembodiment, only four leaf springs are required for proper pumpoperation, although five are provided to provide a margin of safety inthe event one of the springs fails.

The platen (98) has a tab (106), a pair of hinge hooks (108) and alengthwise hole (109). The tab (106) is received within a cavity (110)in the inner recess (94) of the cassette door (50) and secured againstlengthwise movement by a pair of posts (112). The hinge hooks (108)captively receive the hinge pins (92) in the manner best illustrated inFIG. 5 both to secure the platen (98) within the inner recess (94) andto confine the leaf springs (100) within the inner recess (94).

The cassette door (50) further includes at its front a pair of spacedlateral cam surfaces (114) each having a gap (115) at the bottom of thecam surface. A complementary pair of engagement pins (116) on the latch(56) are configured to engage the lateral cam surfaces (114) and drivethe cassette door (50) toward the pump cassette receptacle (84) as thelatch is moved from fight to left, as viewed in FIGS. 6 and 7, and tohold the cassette door (50) shut.

Extending into the pump cassette receptacle (84) through the rigidhousing back (22) are four registration pins (118), a plunger (120), aninlet valve pincher (122), an outlet valve pincher (124), a pressuretransducer button wedge (126) having an arcuate leading edge (127)received between a pair of guide posts (128) and an ultrasonic airdetector (130). The registration pins (118) are made of a rigid materialsuch as aluminum or steel and the plunger (120), the inlet and outletvalve pinchers (122,124) and pressure transducer button wedge (126) arepreferably made of self-lubricating polymer to minimize potentialbinding and to maximize cleanability. At opposite ends of the leadingedge of the inlet and outlet pincher valves are a pair of stops (131)(see FIGS. 9-11A).

The registration pins (118) are configured to engage the platen (98) anddrive its against the bias of the leaf springs (100) into the innerrecess (94) so as to position the platen (98) a select distance from theplunger (120) for reasons which will be discussed in greater detailbelow.

B. Pump Cassette

As seen in FIGS. 5-8A the pump cassette (86) includes an elastomericconduit or a pump chamber assembly (132), a rigid frame (134), a slider(136) and a pincher (138) which are snap fit together. The pump cassette(86) facilitates quick and easy positioning of the pump chamber assembly(132) relative to plunger (120) and inlet and outlet valve pinchers(122,124) as well as an anti-free flow structure.

Referring to FIG. 8A, the elastomeric conduit or pump chamber assembly(132) consists of a pump chamber (140) made of polyurethane tubing, aninlet valve tube or adaptor (142) and an outlet valve tube or adaptor(144) both made of low durometer polyvinylchloride (PVC), and identicalinlet and outlet clips (146,148). Polyurethane was selected for the pumpchamber because of its ability to rebound and its stiffness. Lowdurometer PVC was selected for the inlet and outlet valve tubes becauseit requires relatively little energy to compress so as to completelyocclude the inlet and outlet valve tubes. These material propertiescombine to optimize the pump chamber assembly (132) operation and tominimize battery power required to pump fluid through the pump chamberassembly (132).

The polyurethane pump chamber (140) exhibits greater rebound than PVCtubing typically used in ambulatory infusion pumps. The ability torebound is particularly important with respect to the pump chamberbecause the pumping mechanism relies upon the resilience of the pumpchamber material to return the pump chamber to an uncompressed state,thereby creating a negative pressure for refill of the pump chamber. Therefill cycle is the limiting factor in the pumping sequence for volumeoutput. If the material does not return to its natural state quickenough, then the pump chamber will be underfilled, causing a decrease involumetric output which degrades pump accuracy. The polyurethane is alsostiffer than convention PVC tubing, creating a hydraulically rigidsection that resists volume changes due to system pressure variances. Asa result, the pump chamber (140) resists "ballooning" with an increasedback pressure which could affect output volumes and thus the accuracy ofthe pump. "Ballooning" refers to a condition where extension of theplunger into the pump chamber causes the non-compressed portion of thepump chamber to elastically expand, thereby resulting in a volume ofliquid discharged from the pump chamber which is less than the volume ofliquid displaced by the plunger. To compensate for the stiffer materialand the increased energy required to compress the stiff pump chamber,wall thickness of the tubing has been minimized. In the illustratedembodiment, the polyurethane pump chamber (140) has a durometer of 80shore A, an inner diameter of 0.157 inches and an outer diameter of0.193 inches. Polyurethane has the additional advantage of being readilysolvent bonded to a variety of materials, including PVC.

The rebound of an elastomer is measured by its tan Δ, which is definedas the viscous response divided by the elastic response of the materialat a select temperature. The smaller the tan Δ the greater the reboundpropensity. A desirable material for a pump chamber has a tan Δ whichremains relatively low through the range of operating temperatures. Forthe present invention, the range of operating temperatures is betweenapproximately 32°-110° F. (0°-45° C.).

FIG. 42 is a graph of Dynamic Mechanical Analysis ("DMA") tan Δ versustemperature for a number of materials. PVC tubing is commonly used withperistaltic type pumps. Over the range of operating temperatures, DMAtan Δ of a low durometer PVC varies between about 0.4-0.07 and the DMAtan Δ of a high durometer PVC varies between about 0.4 to 0.2. As can beseen in FIG. 42, the DMA tan Δ of polyurethane ranges between about0.2-0.08. Thus, polyurethane has a lower tan Δ than the tested PVC'sover the range of operating temperatures.

In order to ensure a constant output volume, material stiffness shouldremain relatively constant over the range of operating temperatures. Aconstant stiffness provides a constant energy requirement forcompressing the tubing over the range of operating temperatures and alsoensures that the stiffness required to resist "ballooning" over therange of operating temperatures is maintained.

As appreciated by those skilled in the art, "stiffness" is a function ofstorage modulus and tube geometry. FIG. 43 is a graph of DMA storagemodulus of pump tubing versus temperature for five materials. As seen inFIG. 43, polyurethane has a relatively constant storage modulus of 10⁸dyne/cm² over the range of operating temperatures, meaning it will havea relatively constant stiffness.

It can be observed from the tables that silicone has the desirablefeatures of a relatively constant storage modulus or stiffness and arelatively low tan Δ over the range of operating temperatures. However,silicone is extremely difficult to solvent bond to other materials, andtherefore is not suitable for use as a pump chamber with the presentinvention which requires a bond between the pump chamber (140) and thePVC inlet and outlet valve tubes (142,144), so as to provide pumpchamber and valve tube materials which optimize pump performance.

The inlet valve tube (142) and outlet valve tube (144) each have alesser inner and outer diameter than the pump chamber (140). Asillustrated in FIG. 8A the inlet valve tube (142) and outlet valve tube(144) are telescopically received within the opposite ends of the innerdiameter of the pump chamber (140) and are solvent bonded thereto. Theinlet and outlet valve tubes (142,144) are preferably made of a PVChaving a durometer between 30 and 60 shore A, with a durometer of 50shore A being preferred. Relatively thick walls and a lower durometerare preferred to lessen the energy required to pinch off the lumens ofthe inlet and outlet valve tubes (142, 144). In the illustratedembodiment, the inlet and outlet valve tubes (142, 144) have an outerdiameter of about 0.163 inches and an inner diameter of about 0.083inches.

Other elastomers which are chemically inert with respect to fluids to bedelivered by the pump and which have similar physical characteristics tothe polyurethane pump chamber (140) and the low durometer PVC inlet andoutlet valve tubes may be suitable substitutes for these materials, andare considered to be within the scope of the invention.

FIG. 9 illustrates a cross-section of the inlet valve tube (142)sandwiched between the inlet valve pincher (122) and the platen (98).The outlet valve robe (144) is identical and will not be separatelydiscussed. During operation of the pump, the inlet valve tube (142) isrepeatedly compressed to completely occlude the lumen (150), asillustrated in FIG. 10, and released to return to the partially deformedconfiguration shown in FIG. 9. Low durometer material is chosen for theinlet and outlet valve tubes to minimize the amount of energy requiredto fully close the lumen (150).

FIG. 11A illustrates an alternative embodiment of the inlet valve tube(142A) with a deformed portion (143) intended to lie between the inletpincher valve (122) and the platen (98). The deformed portion (143) hasa football-shaped cross-section (150A), as best viewed in FIG. 11B. Thisshape removes the vertical wall of the tubing (142A) which must becrushed during the closure of the tubing. The tubing (142A) is mountedwithin the frame (134) with the minor axis aligned parallel to thedirections of movement illustrated by arrow (145) between the valvepincher (122) and the platen (98). Thus, the inlet valve tube embodiment(142A) illustrated in FIGS. 11A and 11B further minimizes the energyrequired to occlude the lumen (150A). The inlet valve tube 142 (or 142A)is extruded or molded using conventional techniques. For example,standard tubing can be deformed by any known process such as RF welding,ultrasonic or pressure forming. The outlet valve tube (144) may beidentical to the alternate embodiment of the inlet valve tube (142A) andwill not be separately described.

An inlet clip (146) (which is identical to the outlet clip (148) whichwill not be separately described) is illustrated in detail in FIG. 8B.The inlet clip (146) includes a greater diameter cylindrical portion(146A) and a coaxial lesser diameter cylindrical portion (146B) with anarcuate step (146C) therebetween. The inlet clip further includes alengthwise opening (146D) and open ends (146E) and (146F). Lastly, theinlet clip (146) includes a pair of arcuate gaps (146G) in the greaterdiameter portion separated by a land portion (146H). The arcuate gaps(146G) of the greater diameter cylindrical portion are received in thearcuate channels (166,168) of the rigid frame (134) to secure the pumpchamber assembly (132) to the rigid frame (134) (see FIGS. 6 and 7). Thelesser diameter cylindrical portion (146B) provides a support to theinlet or outlet valve robes (142, 144) to prevent kinking thereof, aswill be discussed below with reference to FIGS. 8C and 8D.

FIG. 8C illustrates bonding of a large bore robe (62) to the clip (146).The large bore tube (62) is axially slid over the valve tube (142) andthe lesser diameter cylindrical portion (146B) and solvent bonded to thelesser diameter cylindrical portion (146B). In addition, the inlet valvetube (142) is solvent bonded to the interior of the inlet clip (146).Solvent bonding of the large bore tubing (62) to the lesser diametercylindrical portion (146) not only provides strain relief in the eventof axial or radial loads on the large bore tube (62), it also preventskinking of the low durometer inlet valve tube (142) so as to decreasethe risk of inadvertent occlusion of the inlet valve tube (142) lumen.In addition, engagement of the large bore diameter tube with the lesserdiameter cylindrical portion in the manner described above provides a"Chinese finger trap" effect which helps to oppose axial removal of thelarge bore tube (62) from the clip (146).

FIG. 8D illustrates connection of a small bore tube (16) to inlet valvetube (142). As illustrated in FIG. 8D, the small bore tube (16) istelescopingly received in the inlet valve tube (142) so as to extendinto the inlet tube lumen at least as far as the small diametercylindrical portion (146B) of the clip (146). In this manner, a strongsolvent bond between the tubes (16, 142) is assured. In addition,insertion of the small bore tube (16) this amount assures the inletvalve tube (142) will not be subject to kinking if a tangential load isapplied.

Referring to FIG. 8A, the rigid frame (134) is molded from athermoplastic resin, preferably ABS. The frame (134) includes a firstlongitudinal member (154), a second longitudinal member (156), an inletend wall (158) and an outlet end wall (160) integrally joined in arectangular configuration. Integral first and second support webs(162,164) having alignment holes (165) (see FIGS. 6 and 7) extendbetween the first and second longitudinal members to improve therigidity of the rigid frame (134). The inlet and outlet end walls(158,160) each defines arcuate channels (166,168), respectively, whichopen in opposite directions. As illustrated in FIG. 8A, the clips(146,148) are received within the arcuate slot (166,168) to secure thepump chamber assembly (132) to the rigid frame (134). Guide channels(170,172) are defined in the support webs (162,164), respectively, tofurther support the pump chamber assembly (132) within the rigid frame(134).

An integral guide rail (174) extends longitudinally along an outer edgeof the second longitudinal member (156). Integrally formed on the secondlongitudinal member (156) proximate the inlet end wall (158) are a pairof ramped bumpers (176) extending in opposite directions from both sidesof the second longitudinal member. A pair of integrally formed pivotpins (178) extend in opposite directions at approximately the center ofthe second longitudinal member (156). An integral pair of ramped camrails (180) extend longitudinally from the second longitudinal member(156) proximate an inner edge and the inlet end wall (158) of the secondlongitudinal member (156). Proximate the outlet end wall (160) anintegral anvil (182) extends from the second longitudinal member (156)toward the first longitudinal member (154). Finally, a pair of integralstops (184) extend in opposite directions transverse of the secondlongitudinal member adjacent to the outlet end wall (160).

The pincher (138) includes a pair of parallel spaced legs (186) eachhaving a pivot hole (188) at one end and a pair of transverse legs (190)joined by a bridge (192) at their other end. A pair of stops (194) (oneshown in FIG. 8) extend lengthwise from the pincher (138) at the base ofeach of the legs (190). Each leg (186) includes a cam surface (196).

The slider (136) has a generally rectangular body (200) having atransverse outwardly extending gripper bar (202) thereon. A pair of legs(204) extend lengthwise from a first end (206) of the rectangular body(200). At a distal end of each of the legs (204) is a romped stop (208)which extends inwardly toward the other leg. At the second end (210) ofthe rectangular body (200) are a pair of lengthwise and inwardlyextending legs (212) each having a camming pin (214) (see FIGS. 6 and 7)which extends inward toward the other of the inwardly extending legs(212).

Assembly of the pump cassette (86) is best understood with reference toFIG. 8A. The pump cassette (86) is assembled by first aligning the pumpchamber assembly (132) with the arcuate slots (166,168)of the end walls(158,160) and the guide channels (170,172) of the support webs (162,164). The inlet clip (146) is then force fit into the open end of thearcuate slot (166) of the inlet end wall (158) and the outlet clip (148)is tucked under the outlet wall (160) and force fit within the arcuateslot (168) of the end wall (160), and both the inlet and outlet clips(146, 148) are solvent bonded in place. With the pump chamber assembly(132) so engaged to the rigid frame (134), any longitudinal strain onthe pump chamber assembly (132) is borne by the clips (146,148) andtransferred to the rigid frame (134), thus protecting the pump chamberassembly (132) from such strains. The pincher (138) is then attached tothe frame (134) by feeding the outlet valve tube (144) between the legs(186) so that the outlet valve tube (144) rests between the transverselegs (190) and the bridge (192). The holes (188) are then positioned toreceive the pivot pins (178) on the second longitudinal member (156). Inthis manner, the pincher (138) is allowed to pivot relative to the rigidframe (134). Finally, the slider (136) is fed onto the guide rail (174)as illustrated in FIG. 8A. More particularly, the second end (210) liesover the guide rail (174) with the camming pins (214) being receivedbetween the ramped cam rails (180) and the cam surface (196) of the legs(186) of the pincher (138). With reference to FIG. 12, as the slider(136) is further slid onto the guide rail (174), the ramped stops (208)engage the ramped bumpers (176), deflecting the legs (204) outwardlywith respect to each other until the romp stops (208) reach the end ofthe ramped bumpers (176), at which point the legs (204) snap inwardlywith respect to each other, securing the slider (136) to the guide rail(174).

C. Anti-Free Flow

The pump cassette (86), the cooperation between the pump cassette (86)and the cassette receiving chamber (84), the door (50), the latch (56)and the inlet and outlet pincher valves (122,124) combine to preventinadvertent free flow during loading and unloading of the pump cassette(86).

With the pump chamber/valve assembly assembled as discussed above, theslider (136) is free to slide back and forth on the guide rail (174)between an open position where the end of the longitudinally andinwardly extending legs (212) abut the base of the transverse legs (190)of the pincher (138) (see FIG. 6) and a closed position where the rampedstops (208) abut the ramped bumpers (176) (see FIG. 7). FIG. 6illustrates the pump cassette (86) with the slider (136) in the "open"position and FIG. 7 illustrates the pump cassette (86) with the slider(136) in the "closed" position. In both FIGS. 6 and 7 the cassette cover(50) is shown cut-away except in the vicinity of the latch (56) forclarity. With the slider (136) in the open position, the camming pin(214) is out of engagement with the cam surface (196) of the pincher(138) and the ramped cam rails (180) of the frame (134). The resilientproperties of the outlet valve tube (144) are thus able to bias thepincher bridge (192) away from the anvil (182) to open the lumen of theoutlet valve tube (144) so as to permit flow of fluid through the pumpchamber assembly (132). As the slider (136) is moved from left to righttoward the closed position as viewed in FIGS. 6 and 7, the camming pin(214) engages the camming surface (196) of the pincher legs (186) andthen further engages the ramped cam rail (180) causing the pincher (138)to pivot downward as viewed in FIG. 7 and illustrated by the arrow (216)so as to pinch the outlet valve (144) and occlude its lumen (150),preventing flow of fluid through the pump chamber/valve assembly.

Referring to FIGS. 13 and 14 the ambulatory infusion pump (10) includesa detent assembly (219) for user convenience to position and maintainthe latch in an "open" position until the cassette door (50) is closed.As seen in FIGS. 4, 5, and 14, within the pump cassette receptacle (84)a cylindrical hole (220) extends into the rigid housing back (22). Asbest seen with reference to FIG. 13, a latch detent piston (222) residesin the cylindrical hole (220). The latch detent piston (222) is biasedupward by a latch detent spring (224) affixed to the rigid housing back(22) within a reduced diameter portion (226) of the cylindrical hole(220). With the latch (56) slid to an open position, the latch detentpiston (222) is received within a cavity (228) in the bottom of thelatch (56) as illustrated by the phantom lines in FIG. 13. The cavity(228) of the latch (56) is formed at one end of an elongate slot (229)(see FIG. 14). With the latch detent piston (222) received in the cavity(228), the latch (56) cannot slide to the left so as to fasten thecassette door (50) closed. A spike (230) extends normally and inwardlyfrom the cassette door (50). As illustrated in FIGS. 4 and 14, with thecassette door (50) closed, the spike (230) is received within thecylindrical hole (220). Referring to FIG. 13, the tip of the spike (230)forces the latch detent piston (222) into the cylindrical hole (220) andout of engagement with the cavity (228) in the bottom of the latch (56),allowing the latch (56) to be slid to the left, as illustrated in FIG.6, with spike (230) received in the slot (229). In this manner theengagement pins (116) come into sliding engagement with the lateral camsurfaces (114) of the cassette door (50) so as to bias the cassette door(50) toward the pump cassette receptacle (84) and to secure the cassettedoor (50) closed.

Loading of the pump cassette (86) into the pump chamber receptacle (84)is best illustrated with reference to FIGS. 5-8A. To load the pumpcassette (86) into the pump cassette receptacle (84), the latch (56) isslid to the fight as viewed in FIGS. 6 and 7 (and to the left as viewedin FIG. 14) sufficiently for the latch detent piston (222) to bereceived within the cavity (228) of the latch (56). This position isillustrated in FIG. 7 and in phantom lines in FIG. 13. As seen in FIG.7, in this position the lateral cam surfaces (114) of the cassette door(50) clear the engagement pins (116) so that the cassette door (50) maybe opened or closed. In addition, in order to insert the pump cassette(86) into the pump cassette receptacle (84), the slider (136) must befully slid to the right (as seen in FIG. 7) and in the closed positionwith the ramped stops (208) abutting the ramped bumpers (176). Only withthe slider so positioned can the gripper bar (202) be received withinthe slot (234) of the latch (56). The pump cassette (86) is receivedwithin the pump cassette receptacle (84) by aligning the gripper bar(202) with the slot (234) of the latch (56) and by aligning theregistration pins (118) with the slots (165) of the support webs(162,164). Alignment of the registration pins (118) with the slots (165)has the desirable effect of precisely positioning the pump chamber/valveassembly with respect to the inlet valve pincher (122), the outlet valvepincher (124), the plunger (120), the pressure transducer button wedge(126) and the ultrasonic air detect (130) to ensure proper conveyanceduring pumping of fluid through the pump chamber/valve assembly anderror detection.

With the pump cassette (86) so loaded, the cassette door (50) can bepivoted downward with the engagement pins (116) received within the gaps(115) at the distal edge of the cassette door (50) proximate the bottomof the lateral cam surfaces (114). At the same time, the spike (230) isreceived within the cylindrical hole (220) forcing the latch detentpiston (222) downward and out of contact with the cavity (228) of thelatch (56). With the lid so closed, the latch (56) can then be slid tothe left, or toward the "locked" position illustrated in FIG. 6. As theengagement pins (116) ride up the lateral cam surfaces (114) the platen(98) is moved close enough to the inlet and outlet valve pinchers(122,124) to fully occlude the inlet and outlet valve tubes (142,144).Only after the inlet and outlet valve tubes (142,144) are occluded isslider (136) moved sufficiently to reach the "open" position illustratedin FIG. 6 wherein the pincher is in a non-occluding position. As thelatch (56) is then moved toward the right as illustrated in FIG. 7, theslider (136) causes the pincher (186) to occlude the outlet valve tube(144) before the inlet or outlet valve pinchers (122,124) ceaseoccluding the inlet and outlet valve tubes. In this manner, free-flowthrough the cassette is prevented during loading and unloading of thecassette.

As the cassette door (50) is closed, the platen (98) is forced into theinner recess (94) of the cassette door (50) by the registration pins(118). The platen is thereby spaced from the piston (120) so the spacebetween the piston (120) surface and the platen varies between preciseselect distances with the piston fully extended and the piston fullywithdrawn to ensure a uniform discharge and full volume of the pumpchamber during a pumping cycle. The floating platen and registrationpins cooperate to eliminate "tolerance stocking" between the platen (98)of the cassette door (50) and the pump driving mechanism (250).

The cassette (86) can be inserted into the pump cassette receptacle (84)and the cassette door (50) subsequently closed only with the slider(136) initially in the "closed" position and the outlet valve tube (144)pinched shut, thereby preventing inadvertent free flow of fluid to apatient during loading of the cassette (86). If the slider (136) is notin the closed position upon loading the cassette (86), the cassette door(50) will be prevented from closing because the engagement pins (116)will strike the lateral cam surfaces (114) of the cassette door (50).This feature assures that at least one of the inlet or outlet pinchervalve pinchers (122,124) will be occluding the lumen of the inlet oroutlet valve tubes (142,144) when the door (50) is closed and the latch(56) is moved from the open to the closed position, again preventinginadvertent free flow of fluids to a patient.

D. Pumping Mechanism

The ambulatory infusion pump includes a pump driving mechanism (250)generally illustrated in FIGS. 15 and 16 which acts on the pump chamberassembly (132) to propel fluid therethrough. The pump driving mechanism(250) is generally illustrated in FIGS. 15 and 16 and includes anassembly frame (252) to which the valve motor (254) and the plungermotor (256) are attached. The assembly frame (252) includes a centralboss (258), a plunger motor support boss (260), a valve drive shaftsupport boss (262), an inlet valve support boss (264), an outlet valvesupport boss (266), and an intermediate valve support boss (268).

The valve motor (254) is a DC electric motor secured to the central boss(258) with the valve drive shaft (270) received in bushings (271,272) inaxially aligned bores (273,274) in the central boss (258) and the valvedrive support boss (262). A crank career (275) rides on the valve driveshaft (270) between the central boss (258) and the valve drive supportboss (262) and a flag ring (276) having a knurled finish surrounds theouter periphery of the crank carrier (275). A set screw (278) securesthe flag ring (276) to the crank carrier (275). A pair of 90° off-setscrews (279) secure the valve drive shaft (270) and the tip of the setscrews (279) engage corresponding 90° off-set flats (280) on the valvedrive shaft (270) to prevent rotation between the drive shaft (270) andthe crank carrier (275). An inlet valve bearing (282) and an outletvalve bearing (284) are attached to the crank carrier (275) by a pair ofpress pins (286) and are spaced from the crank carrier (275) by washers(288). In this manner the bearings (282,284) may spin freely about thepress pins (286).

An inlet rocker arm (290) is mounted between an orifice (291) in theinlet valve support boss (264) and an orifice (not shown) in theintermediate valve support boss (268) by an inlet valve shaft (292)received within an inlet valve shaft envelope (294) of the inlet rockerarm (290) and is secured thereto against relative motion by the pin(295). Bushings (296,297) in the orifices (291,293) provide for smoothrotation of the shaft (292). An inlet valve cam (298) extendstransversely from a front end of the inlet valve shaft envelope (294)with its distal end received around the bearing (282). A valve actuator(304) extends transversely from a second end of the inlet valve shaftenvelope (294). An outlet valve rocker arm (305) is mounted between anorifice (306) in the outlet valve support boss (266) and an orifice inthe intermediate valve support boss (268) about an outlet valve shaft(307) received in the outlet valve shaft envelope (308) and the outletvalve envelope (308) is secured against rotation relative to the outletvalve shaft (307) by the pin (309). A bushing (310) in the outlet valvesupport boss orifice and a bushing (not shown) in the intermediatesupport boss orifice provide for smooth rotation of the shaft (307). Anoutlet valve cam (311) at a first end of the outlet valve envelope (306)receives the bearing (284) at its distal end. At the second end of theoutlet valve envelope (306) is an outlet valve actuator (313).

FIG. 17 illustrates the crank carrier (275), the valve motor shaft(270), the inlet rocker arm (290) and the outlet rocker arm (305) in a"neutral" position with the inlet valve pincher (122) and outlet valvepincher (124) biased closed. As seen in FIG. 17, the inlet valve bearing(282) is located on an opposite end of the crank carrier (275) from theoutlet valve bearing (284), and the inlet valve bearing and the outletvalve bearing are located on radii extending 180° from each other.

FIG. 18A is taken from the perspective of the left-hand side of theinlet valve cam (298) as viewed in FIG. 17. The inlet valve cam (298)includes a first leg (299) and a second leg (300) defining an arcuatesurface (301) therebetween. The outlet valve cam (311) is configuredidentical to the inlet valve cam (298), which simplifies manufacture ofthe pumping mechanism. The arcuate surface (301) forms a dual cam (302)having a first cam surface (302A) and a second cam surface (302B)proximate the distal end of the first leg (300). The dual cam surface(302) is configured so that as the crank carrier (275) is rotatedclockwise from the valve neutral position from the perspective of FIG.18A, the first cam surface (302A) is engaged by the outlet valve beating(284) causing the outlet valve cam (311) to lift the outlet pinchervalve (124). The arcuate surface (301) proximate the first leg (299) isconfigured so that the inlet valve bearing (282) kisses the arcuatesurface (301) without causing movement of the inlet valve cam (298). Ina like manner, when the crank carrier (275) is rotated clockwise fromthe valve neutral position from the perspective of FIG. 18A, the secondcam surface (302B) is engaged by the inlet valve bearing (282), causingthe inlet valve cam (298) to lift the inlet pincher valve (122).

Referring to FIGS. 15 and 16, the plunger motor (256) is a DC electricmotor attached to the plunger motor support boss (260) with the plungerdrive shaft (316) received within the axially aligned holes (318,320) inthe plunger motor support boss (260) and the central boss (158),respectively. Bushings (321,322) facilitate rotation of the plungerdrive shaft (316) within the holes (318,320). Mounted about the plungerdrive shaft (316) is a plunger cam (323) nested between the central boss(258) and the plunger motor support boss (260) and held in place by apair of 90° offset screws and corresponding flats (not shown). Theplunger cam (323) has a flag or mechanical stop (324) integrally formedbetween a least diameter portion (325) and a greatest diameter portion(326) of the plunger cam surface. Beginning at a "home" position withthe plunger fully retracted, the DC electric plunger motor (256)oscillates approximately 194° in a first direction, thereby engaging thegreatest diameter portion (326) of the plunger cam (322) with theplunger (120) to extend the plunger (120) so as to compress the pumpchamber (140). The plunger motor can reverse direction and rotate theplunger cam (322) up to 200° in a second direction opposite the firstdirection until the flag (324) couples the optosensor (410), therebyreturning the plunger to the "home position" by engaging the leastdiameter portion(325) of the plunger cam (322) with the plunger (120),allowing the pump chamber (140) tubing to bias the plunger (120) to itsfully retracted position. Runaway is prevented by the mechanical stop(324) of the plunger cam (322) abutting the assembly frame (252) tomechanically stop rotation of oscillating plunger motor (256) in theevent of a system failure.

The ambulatory infusion pump (10) uses a separate valve motor (254) andplunger motor (256) to allow for the independent control and timing ofthe valves and the plunger. In addition to making the fail-safereciprocating action discussed above possible, the use of two motorsallows each motor to be optimized for its own selected task. In thismanner, the motors are more energy efficient than attempting to use onemotor for both plunger and valve actuation. The use of two motors alsoallows independent control of the plunger and valves, a feature which isused to perform a number of self-test red self-compensating functionsand to facilitate delivery of fluid at different rams through differentpump modes employing a number of distinct plunger and valve actuationsequences, all of which will be discussed in greater detail below.

As seen in FIG. 16, inlet and outlet valve assemblies (330,330A) includea valve pincher mount (332) received within a valve guide (334) with avalve washer (336) and a compression spring (338) axially nestedtherebetween. The valve guide (334), in turn, is attached to theassembly frame (252) where indicated in FIG. 16. The compression spring(338) biases the mount valve pincher (332) away from the assembly frame(252) to an extended position for occluding the inlet or outlet valvetubes (142,144). In addition, a C-spring or leaf spring (340) isreceived in a slot (342) of the inlet valve guide (334) and acts on theproximal end (344) of the valve pincher mount (332) to further bias thevalve pincher (332) away from the assembly frame (252) to an occludingposition. The leading edge of each of the inlet and outlet valvepinchers (122,124) has a small radius of 0.03 inches. This small radiusminimizes the energy necessary to occlude the inlet and outlet valvetubes (142,144) while minimizing kinking of the tubing during occlusion.In addition, as most clearly seen in FIG. 10, the stops (131) atopposite ends of the leading edge of the inlet valve pincher (122) (and,though not separately illustrated, on the outlet pincher (124)),maintain a 0.04 inch gap between the pincher valve and the platen whichfurther minimizes tube kinking while the tubes are occluded. Either ofthe compression spring (338) or the C-spring (340) provides sufficientbias to the valve pinchers (122,124) to occlude the inlet and outletvalves (142,144), thus providing an added margin of safety. Furthermore,this spring bias ensures that if power to the pump is cut off, thevalves will return to a neutral position occluding the inlet and outletvalves (142,144) or, if either valve is in the over center position whenthe power is cut-off, the valve will remain open and the other valvewill be biased closed.

A plunger assembly (350) includes the plunger (120) having a back (352)with a pair of bosses (354) which receive a cam follower or ball bearing(356) therebetween, the cam follower (356) being maintained in place byan eccentric (358) for calibration of the plunger position. The plungercam (323) acts on the cam follower (356) to drive the plunger upward asthe plunger cam (323) rotates in a counter-clockwise direction withreference to FIG. 19.

A pressure transducer (362) is received in a stepped hole (364) in theassembly frame (252). A transducer backing plate (366) is fastened tothe assembly frame (252) by screws (368) to maintain the pressuretransducer (362) in a fixed position. A transducer button (368) is alsoreceived within the stepped hole (364) and extends outwardly from theassembly frame (252) opposite of the pressure transducer (362) so thatthe transducer button wedge (126) can extend between the guide posts(128) into the pump cassette receptacle (84).

A gasket (370) made of a molded silicone rubber has an inlet valvepincher orifice (372), an outlet valve pincher orifice (374), a plungerorifice (376) surrounded by a raised collar (377), a transducer buttonorifice (278), and four registration pin orifices (380). The transducerbutton (368) is inserted through the pressure transducer orifice (378)so that the flange (381) is on the frame side of the gasket. The plunger(120) is inserted into the plunger orifice (376) such that the gasketsits in a slot in the frame (252) around the plunger (120). Theregistration pins (118) are fixedly attached to the bottom of theassembly frame (252) and are received within the registration pinorifices (380) of the gasket (370). The gasket (370) is then stretchedso that the inlet and outlet valve pinchers (122,124) are receivedwithin the inlet and outlet pincher orifices (372,374) and the gasket ispress fit against the frame. The gasket (370) functions as a face sealbetween the inner surface of the rigid housing back 22 and eachcomponent. The raised collar (377) functions to resiliently bias theplunger (120) toward the frame (252) to maintain the cam follower (356)in contact with the plunger cam (323) even if the door (50) is open orno cassette (86) is in the cassette receptacle (84).

FIGS. 18A-D illustrate actuation of the inlet and outlet valve pinchers(122,124) by the valve motor (254). As the crank carrier (275) isrotated counterclockwise with respect to FIG. 18A, the inlet valvebearing (282) engages the second cam surface (302B), actuating the inletvalve (298) against the action of the spring (338) and C-spring (340) soas to open the inlet valve tube (142). Although not illustrated, withthe valve carrier so rotated, the outlet valve bushing (284) kisses thearcuate surface (301) proximate the first leg (299) of the outlet valvecam (310), thereby exerting no force on the outlet valve cam (311). Asthe outlet valve bearing (284) disengages the first cam surface (302A),the outlet valve cam (311) is biased upwards by the force of the springs(338) and (340). However, should the outlet valve become stuck in anopen position contrary to the bias of the springs (338) or (340), theoutlet valve bushing (284) will forcibly contact the arcuate surface(301). This may have the effect of dislodging the outlet pincher valve(124) from the non-occluding position or, more likely, it will result inan increased draw of energy on the valve motor, thereby triggering analarm (see Section F below).

FIGS. 18B-D serve to illustrate an over center feature of the valvedriving mechanism. FIG. 18C illustrates the inlet valve cam (298) in thevalve neutral position. FIG. 18D illustrates that the crank carrier isrotated clockwise from the valve neutral position of FIG. 18C. The inletvalve bearing (282) kisses the arcuate surface (301) proximate the firstleg (299) of the inlet valve cam (298). Concurrently, the outlet valvebushing (284) engages the first cam surface (302A), thereby actuatingthe outlet valve cam (311) and fully opening the outlet pincher valve(124) after 90° of rotation. The crank carrier (275) is rotatableapproximately an additional 10° clockwise to an over center positionillustrated in FIG. 284D, whereupon the outlet valve bushing (284)engages the stop (312). At the over center position, the outlet valvecam (311) is "locked" in position against the bias of the springs (338)and (340). The valve motor rotates the crank carrier (275)counterclockwise back to the valve neutral position illustrated in FIG.18C. Further rotation of the crank carrier (275) 90° counterclockwisewill cause the inlet valve bearing (282) to engage the second camsurface (302B), actuating the inlet valve cam. (See FIG. 18B) As withthe outlet valve assembly, rotation an additional 10° will "lock" theinlet valve can (298) in an over center position. Accordingly, if powerto the valve motor is cut off, three valve positions are possible: 1)crank carrier halted over center with the outlet valve open and theinlet valve closed; 2) crank carrier halted in the valve neutralposition with both valves closed; or 3) the valve carrier halted in anover center position with the inlet valve opened and the outlet valveclosed. Thus, at least one valve is always closed, preventingunintentional free flow. It should be noted that at high pump rates, thevalve motor does not pause with the crank carrier in the valve neutralposition.

E. Position Sensor/Magnetic Detent

As will be discussed below with reference to FIG. 32, the pump (10)includes an electronic control (385) which actuates the pumping assembly(250) and receives signals from a variety of sensors to monitor pumpperformance.

The plunger motor (256) is shown in an exploded perspective view in FIG.20 to illustrate a Hall sensor/magnetic detent assembly (387) forpermitting precise monitoring of the plunger position and formaintaining the plunger in a precise position when the plunger motor isnot energized. A motor drive shaft (388) extends opposite the plungerdrive shaft (316) from the body (390) of the plunger motor (256). Fixedto the motor drive shaft (388) for rotation with the motor drive shaftis a rotary cylindrical Neodymium-Yag magnet (392). Radially spacedabout the periphery of the rotary magnet (392) is a ferrimagnetic collar(394), the ferrimagnetic collar being made of soft iron in the presentembodiment. Integrally formed in an inner surface of the ferrimagneticcollar (394) is an inwardly extending flux collector (396). Located onthe ferrimagnetic collar (394) opposite the flux collector (396) are apair of spaced bosses (398) extending inwardly from an inner surface ofthe ferrimagnetic collar, the bosses being spaced to receive a Hallsensor (400) therebetween. A shell (402) is provided for encasing theHall sensor/magnetic detent assembly (387). As generally understood bythose skilled in the art, the Hall sensor (400) is used to sense theposition of the motor drive shaft (388) so that the correspondingposition of the plunger (120) can be precisely monitored. Moreparticularly, the Hall sensor (400) sends a signal to the control (385),once each revolution of the shaft (388), so that the control (385) cantrack the precise location of the plunger (120).

The flux collector (396) cooperates with the magnet (392) to function asa magnetic detent. More particularly, when the motor (256) isdeenergized, rotation of the motor shaft (388) will be resisted byattraction of the poles of the magnet (392) to the flux collector (396).This attraction or detent feature provides sufficient resistance torotation of the shaft (388) that the plunger (120) can be maintained ina selected position notwithstanding the pump chamber (140) biasing theplunger (120) to retract. That is, the detent provides sufficientholding torque with the motor turned "off" during a sleep sequence toprevent back driving of the plunger. In this manner, the DC electricmotor (256) functions like a stepper motor in that its shaft can bestopped at precise locations. However, the DC electric motor maintainsthe advantage of being significantly more energy efficient andlightweight than a stepper motor. In addition, when the shaft (388) isrotated at high speeds, the magnetic detent effect becomes "transparent"in the sense that vibration of the motor is minimized.

F. Other Sensors

As seen in FIG. 16, in addition to the Hall sensor/magnetic detentassembly (387), the plunger motor (256) includes a sensor (404) formonitoring motor current, the sensor (404) producing an electricalsignal proportional to the motor current. The control (385) monitors theelectrical signal to ensure a high current which indicates a jam orother abnormal condition is not present. If such an abnormal conditionis present, the control (385) activates an alarm.

The valve motor (254) also includes a Hall sensor (406) for producing anelectric signal with each revolution of the valve motor drive shaftwhich is similar to the Hall sensor/magnetic detent (287) of the plungermotor, only lacking the flux collector (297) and therefore the magneticdetent feature of the Hall sensor/magnetic detent (387) of the plungermotor (256). In addition, a valve motor sensor (408) produces anelectrical signal proportional to the current drawn by the valve motor(254), which is monitored by the control (385) as discussed above withrespect to the plunger motor (256).

Optical position sensors are also included as part of the plunger andvalve drive for the purpose of monitoring the position of the plunger(120) and the inlet (122) and outlet (124) valves. A plunger opticalsensor (410) (see FIGS. 15, 16 and 19) includes a light emitting diode(411) and a photodetector (412) (FIG. 19). With the plunger cam rotatedto its "home" position as illustrated in FIG. 13, the plunger cam flag(324) causes a coupling between the light emitting diode (411) and thephotodetector (412) which in turn causes the cam position sensor (410)to send an electric signal to the control (385) indicating that theplunger cam (323) is in its "home" position, corresponding to theplunger (120) being in a "retracted" position. As the plunger cam (323)actuates the plunger (120) out of the home position illustrated in FIG.13, the light emitting diode (411) and photodetector (412) are uncoupledand the LED and photodetector can be turned off to save power. If turnedoff, the LED and photodetector are repowered when the control (385)determines, by virtue of signals received from the Hall sensor (400),that the plunger cam has returned to the home position.

A valve optical sensor (415) is located where indicated in FIGS. 16 and18A-D. The flag ring (276) has a black anodized outer surface with anon-coated reflective window (417). The valve optical sensor includes anLED and a photodetector, not separately shown. When the reflectivewindow (417) aligns with the optical sensor, the LED) and thephotodetector are "coupled", causing generation of an electric signalwhich is sent to the control (385). The reflective window (417) alignedwith the valve optical sensor (415) corresponds to a "neutral" positionof the valve motor crank (270), meaning that both valves are closed.When the reflective window is rotated out of alignment with the valveoptical sensor, the LED and photodetector are uncoupled and the valveoptical sensor is turned off to conserve power. The position of thewindow (417) is adjusted during calibration of the pump to preciselycorrespond to the neutral position by loosening of the set screw (278)and rotation of the flag ting (276) relative to the crank carrier (275).

The plunger optical sensor (410) and the valve optical sensor (415) areused in conjunction with the plunger motor Hall sensor (400) and thevalve motor Hall sensor (406) to precisely monitor the location of theplunger and the inlet and outlet valves relative to their home andneutral positions, respectively. More particularly, the optical sensorsare used by the control (385) to define the home and neutral position ofthe plunger and valve. The Hall sensor provides a much finer resolutionfor locating the plunger and valve relative to the home and neutralpositions. For example, with respect to the plunger, twenty-fiverevolutions of the motor are required to fully extend the plunger fromits home position. Each revolution of the motor results in one signalfrom the plunger motor Hall sensor (400), therefore counting of thesignals from the Hall sensor by the control (385) permits preciselocation of the plunger. Thus, the plunger and valve optical sensors(410,415) are used by the control (385) to verify the accuracy of theposition determined based upon the Hall sensors, to calibrate positionof the plunger and valves, by being turned on and off by the control(385), to conserve energy.

The pressure transducer (362) is operatively linked to the pump chamber(140) by the button wedge (126), as best seen in FIGS. 4 and 16. Thepump chamber (140) is received between the guide posts (128) whichensures that the arcuate leading edge (127) of the button wedge (126)compresses the pump chamber against the platen (98) in the mannerillustrated in FIG. 21, thereby minimizing the propagation of "noise"signals which would otherwise effect the accuracy of the transducer(362). Pressure fluctuations within the pump chamber result in adisplacement of the button wedge (126) which is detected by thetransducer (362). The transducer (362) produces an electric signalrepresentative of the pressure in the pump chamber (140) which istransmitted to the control (385). The control (385) monitors pressure inthe pump chamber to check for insufficient pump chamber refill, valveleakage or downstream occlusion, as will be discussed in greater detailin Section N2 below.

A cassette door sensor (420) is illustrated in FIG. 3. It is a magneticproximity sensor which monitors when the cassette door (50) is properlyengaged to the rigid housing back (22). More particularly, the doorsensor (420) sends an electric signal to the control (385) when latch(56) is a "closed" position. When such a signal is received, the control(385) permits pump operation.

A front cover sensor (422) (see FIG. 2) is a magnetic proximity sensorwhich detects when the front cover (24) is slid down to uncover theprogrammer display (28) and keyboard (30). When the control panel (26)is opened a sufficient distance, the front cover sensor will send anelectric signal to control (385), causing the control (385) to energizea programming display (228). When the front cover (24) is closed and theelectric signal is no longer received, the control (385) deactivates theprogrammer display (28) to conserve power.

The ultrasonic air detector (130) (see FIG. 4) is provided for ensuringthat excessive air is not delivered with the liquid medication to apatient. The ultrasonic air detector (130) includes a conventionalpiezoelectric ultrasonic transmitter and receiver spaced apart on bothsides of the inlet valve tube (142). The transmitter and receiver arespaced slightly less than the outer diameter of the inlet valve tube(142) to assure that the inlet valve tube (142) fits snuglytherebetween. The finger (423) extends from the door (50) and receivedbetween the transmitter and receiver (130) to force the inlet valve tube(142) between the transmitter and receiver (13) upon closing the door(50) and to secure the inlet valve tube (142) therebetween. Thetransmitter produces an ultrasonic signal that is transmitted through aninlet valve tube (142) to the receiver. Liquid present in the inletvalve tube (142) between the transmitter and the receiver conveys theultrasonic signal much more efficiently than does an air bubble. Thereceiver produces and transmits to the control (385) an electric signalin response to the level of the ultrasonic signal it receives, theamplitude of the electronic signal indicating whether an air bubble orliquid is present in the inlet valve tube (142) between the transmitterand the receiver. During refill of the pump chamber, an ultrasonicsignal is produced once each motor revolution. Only if the signalreceived by the control (385) indicates that an unacceptable level ofair is present for a select number of consecutive refill revolutionswill an alarm indicating air in the pump chamber be triggered. The airdetect routine of the control (385) is discussed in further detail inSec. N2.

G. Soft Pump Case

The soft pump case (12) is shown in detail in FIGS. 22-24. The soft pumpcase (12) is made of fabric such as a waterproof nylon and includes apump receiving chamber (440) and a solution bag receiving chamber (442)joined by an integral hinge (444). The pump receiving chamber (440) andthe solution bag receiving chamber (442) are joinable in an abutting andoverlying relationship by a zipper (446). The zipper (446) includes afirst slider (448) and a second slider (450) and first and second stops(452,454). As illustrated in FIG. 17, with the first and second sliders(448,450) positioned with the zipper teeth engaged, they come intoabutment with the first and second stops (452,454) to define a gap (456)through which the IV tube (16) can extend from the soft pump case (12).The second slider (450) causes approximately three-quarters of thezipper teeth to become engaged and disengaged and the first slider (448)causes less than a quarter of the zipper teeth to become engaged anddisengaged.

The pump receiving chamber (440) includes four side walls (458) and abottom wall (460) with the zipper teeth at the distal end of the sidewalls (458). An elastic retention strap (462) extends across the bottomwall (460) for securing the ambulatory infusion pump (10) within thepump receiving chamber (440). Alternatively, a hook and loop strap couldreplace the elastic retention strap (462). A variety of holes areprovided in the side walls (458) of the pump receiving chamber to allowfor access to the pump controls. For example, the hole (464) providesaccess to the on/off switch (76), a hole (465) provides access to the IRwindow (70) and a grommet (467) provides access to the remote bolusswitch contact (42) (see FIG. 23). A clear plastic membrane preferablycovers the hole (464) to protect the ambulatory infusion pump (10) fromdirt and moisture. FIG. 23 illustrates a panel (466) which provides foraccess to the user control panel (32). In one embodiment, the panel(466) is covered with a clear plastic membrane to allow for observationof the patient display (36) as well as access to the control buttons onthe beveled front surface (34) of the pump 10. A cover (468) canselectively cover or expose the panel (466) and is preferably secured tothe exterior of the pump receiving chamber (440) by a hook and loopconnector (470) such as Velcro®.

The solution bag chamber (442) includes a partition (472) defining apocket (474) for receiving the solution bag (64). A pair of straps (74)are on the exterior of the solution bag chamber (442) for fastening thesoft pump case to an upright support such as a patient's belt (see FIG.1).

As illustrated in FIG. 16, with the solution bag (64) received in thepocket (474), the solution bag outlet orifice (68), including the spike(66), can be folded over the solution bag (64) and the partition (472).The solution bag chamber (442) can then be folded over the pumpreceiving chamber (440) in a book-like fashion so that the first andsecond sliders (448,450) can engage the teeth of the zipper (446) toclose the soft pump case (12). With the soft pump case so closed, theambulatory infusion pump (10) can be attached to a patient by the beltloops (74) (see FIG. 24) for convenient travel with the patient. Thesolution bag is located between the rigid front and back housings(20,22) of the ambulatory infusion pump (10) and a patient's body,thereby protecting the solution bag (64) from damage. In addition, thefluid within the solution bag (64) is maintained at or near thepatient's body temperature. This improves pump accuracy because changesin viscosity resulting from changes in liquid temperature are minimized.Furthermore, the solution bag provides padding between the patient andthe pump, enhancing patient comfort.

H. Pump Displays and Delivery Profiles

The control panel (26) and beveled front surface (34) are shown ingreater detail in FIG. 25. A sample patient display (36) is illustratedin FIG. 26. The patient display shows user information through fixedsegments or icons (510). For example, in FIG. 26 the "COMPLETE KVO" iconmeans that the current infusion has ended and the pump is now running atthe Keep Vein Open (KVO) rate. Volume remaining in a medication supplyis shown at (512). Lines (514) are sequentially illuminated to provide auser immediate confirmation that the pump is pumping.

The programming display (28) is used for data entry and displayingstatus information to a clinician. The three major screens which theclinician will see are the select delivery mode (FIG. 27), set up (FIG.28) and status (FIG. 29).

A sample select delivery mode screen (516) is illustrated in FIG. 27.Each of the five delivery profiles (517), which are discussed in thissection below, are listed: 1) continuous; 2) continuous with patentcontrolled analgesia (PCA); 3) continuous with taper; 4) intermittent;and 5) intermittent with bolus.

A sample setup screen (519) is illustrated in FIG. 28. A distinct setupscreen is displayed for each delivery profile (517). An icon (520)indicates the appropriate delivery profile. Here, the setup screen isfor continuous infusion with a PCA. Using the keyboard (30), a cliniciancan enter values for each of the input options (521), as discussed ingreater detail below. For example, the reservoir volume, medicationconcentration, the rate at which the drug is to be infused based uponthe concentration rate, the PCA dose, and the lockout period and anauthorized clinician bolus can all be entered.

A sample programming display screen for the mode status (532) isillustrated in FIG. 29. An icon (533) illustrates the selected pumpingmode. There the icon (533) stands for intermittent administration withbolus. Current pump operating status is shown at (534). The status ofany alarms or alerts is shown at (536). The volume of solutionremaining, volume of solution delivered, the dose rate, the keep veinopen KVO) rate, the bolus dose and the number of bolus doses tried anddelivered are displayed at (537). It should be understood that theparticular parameters displayed in the setup and status screen vary withthe pump mode which is currently selected.

FIGS. 37A-E illustrate the five delivery profiles. Particularly, FIG. 37A illustrates the "continuous" flow profile. A continuous flow rateentered at the setup screen is administered for a time selected at thesetup screen. Following the selected continuous flow, the pump deliversthe KVO rate until the infusion ends.

FIG. 37B illustrates the "continuous" flow with taper profile. The setupscreen requires entry of the reservoir volume, total time of delivery,the taper up time, the taper down time, and the continuous rate ofinfusion. The monitor microprocessor calculates the taper up and taperdown rates as follows. First, the continuous flow rate establishedbetween the taper up and taper down operations is calculated. Thedifference between the continuous flow rate and the KVO rate is dividedby the number of minutes in the taper operation to obtain an amount thatthe rate will change each minute. For example, if the continuous flowrate is 140 ml/hr, the KVO rate is 20 ml/hr and the taper rate is sixtyminutes, then the rate will change by (140-20)/60 or two ml/hr for eachminute. For taper up operation, the first minute the pump will deliver22 ml/hr. At the end of the first minute, the pump will switch to a rateof 24 ml/hr., et cetera. This minute by minute rate stair step willcontinue until sixty minutes has elapsed and the continuous flow rate of140 ml/hr. has been obtained. In a similar manner, the rate changes eachminute to stair step down from the study state flow rate to the KVO rateover the taper down time period. During each minute the rate isdelivered in ate manner normal for that rate within the pump. That is,one of flow modes 1-5, which corresponds to the required flow rate (seeSection N below), is called by the main control routine.

FIG. 37C illustrates the "continuous flow with PCA". At the setupscreen, the user enters reservoir volume, concentration units,concentration rate, PCA dose, lockout period and clinician bolus. Asseen in FIG. 37C, the clinician bolus is administered. Thereafter, acontinuous flow is administered in accordance with the selected rate.During continuous flow, the patient may administer PCA dose througheither the remote PCA button (44) or the PCA button (40) on the patientpanel. Following administration of the PCA, the flow rate returns to thecontinuous flow rate and the lockout is reset. The patient is againprevented from administering PCA until the conclusion of the lockoutperiod. The clinician bolus, continuous flow and PCA rates are deliveredin accordance with the pump mode dictated by the required rate of flow.At the conclusion of the; continuous flow period, delivery returns tothe KVO rate.

FIG. 37D illustrates the "intermittent delivery" profile. The setupscreen requires entry of the reservoir volume, the dose rate, the timeat dose rate, the KVO rate, the dose interval, the delay before start ofthe first dose administration and the start time. Between dose rates,the pump returns to the select KVO rate.

FIG. 37E illustrates the "intermittent with bolus" delivery profile. Theintermittent with bolus delivery profile requires entry of the reservoirvolume, the dose rate, the time at dose rate, the KVO rate, the doseinterval, the allowed bolus dose, the lockout period, the delay periodand, if desired, the clinician bolus. As illustrated in FIG. 37E,following the clinician bolus, the pump delivers at a KVO rate and alockout period begins. At the conclusion of the lockout period, whichcan be of variable length, including zero, a bolus may be administered.The dose rate is administered after a set interval, following which thelockout period is again reset and a delivery is conducted at the KVOrate. Once the lockout period has again elapsed, a bolus dose may beagain administered.

I. Programmer Controls

The keyboard (30) includes up/down buttons (522) which are used forscrolling between various delivery modes in the select delivery modescreen (516) illustrated in FIG. 27, scrolling between different inputoption (521) of a set-up screen (519) illustrated in FIG. 2 and forscrolling through values for each of the input option (521). A selectkey (523) allows selection of a delivery mode (517) scrolled to usingthe up and down keys (522), selection of an input option (521) for entryof a value or to deselect and enter a given value scrolled to using theup down keys (522) for a given input option (521). The finished programkey (524) is used to enter a completed set-up screen (520) after entryof values for each selected input option. The edit/view key (525) allowsa user to go from a mode status screen (532) of FIG. 29 to the setupscreen (520) illustrated in FIG. 28. A Change Mode button (526) enablesa user to go from the mode status screen (532) to the select deliverymode screen (516) of FIG. 27. The cancel key (527) cancels editing of aset-up screen (520) for a selected delivery mode and returns theprogramming display (28) to the last mode status screen. The historybutton (529) allows the clinician to view the history while the pump isin the standby state. A sample pump history screen (539) is contained inFIG. 30. The pump history displays such information as the total numberof pumping events currently in the history log, an event numberindicating what pump event is currently being viewed, date and timefields to indicate the date and time of the occurrence of the currentlyviewed event, and a description of the currently viewed event. The printbutton (530) can be actuated only when the pump is in the standby stage.The entire pump history can be printed by pressing the "print" button(530) once. Pushing the "print" button twice will cancel the print. Theprime button (531) can be pressed following loading of the pump cassetteinto the pump for priming the pump. Pressing the prime button causespumping of approximately 3.0 ml of fluid through the pump chamber.

J. Pumping Action

Operation of the plunger and valves to pump fluid through the pumpchamber/valve assembly is best understood with reference to FIGS. 31A-D.Each of FIGS. 31 A-D includes the pump platen (98); the pump/valveassembly (132), consisting of the pump chamber (140) and the inlet andoutlet valve tubes (142), (144); the inlet valve pincher (122); theoutlet valve pincher (124); and the plunger (120). As discussed inSections N2-6, combinations of movement of the plunger (120) and inletand outlet valves (122,124), as illustrated in FIGS. 31A-D, provide agreat degree of flexibility in delivery rates (0.1 ml/hr-390 ml/hr) anddelivery profiles.

FIG. 31A illustrates the pump chamber/valve assembly in a refillposition with the outlet pincher valve (124) occluding the outlet valveto (144) and the inlet valve (122) open. The plunger (120) is in a fullyretracted position, or position "-1". While fully retracted, the plunger(120) partially compresses the pump chamber (140). A scale "A" isincluded in FIG. 31A to represent 26 incremental advancements of theplunger (120), each advancement resulting from a revolution of theplunger motor (256).

FIG. 31B illustrates the plunger advance one increment to position "0".Advancement of the plunger between the positions illustrated in FIG. 31Aand FIG. 31B is known as a compensation step which is used to ensurethat at position "0" the pump chamber is filled with a precise selectamount of fluid.

FIG. 31C illustrates a position of the valves and the plunger during afill and valve leak test sequence. In this configuration, both the inletand outlet pincher valves (122), (124) are extended to occlude fileinlet and outlet valve tubes (142), (144) and the plunger (120) isadvanced three motor revolutions so that pressure within the pumpchamber can be measured by the transducer button wedge (126). The filland valve leak test is described in greater detail in Section N.7.

FIG. 31D illustrates the discharge of the pump chamber (140) with theoutlet pincher valve (124) open and the inlet pincher valve (122)closed. In FIG. 31D the plunger (120) is illustrated at position "25",extended 25 increments or motor revolutions from the "0" or homeposition. With the plunger (120) fully extended, the pump chamber (140)is not fully compressed. As also viewed in FIG. 31D the pump chamber inFIG. 31D expands somewhat into the lengthwise hole (109) in the platen(98) so as to assure a more consistent pump discharge volume.

K. Pump Electronics.

With reference to FIG. 32, a block diagram illustrates an electricalcircuit for the pump (10) of FIG. 1.

The pump incorporates a dual microprocessor design. The use of twomicroprocessors provides a great deal of design flexibility instructuring two different software packets to check and balance criticalfunctions, and splits the work assignments on non-critical functions.The two processors have segmented functions, and different software, andare not running the same software in parallel. Their clocks are run atdifferent frequencies to avoid errors related to single time basecalculations. Critical functions, such as cam position timing signifyingend of stroke, are predicted and checked by two different algorithms andsoftware routines. The results must match, and serial communication mustoccur appropriately between the microprocessors to continue operation.Each microprocessor can stop the motors and sound an alarm ifcommunications cease, are in error, or a fault condition is detected.

The two microprocessors comprise a monitor microprocessor (540) and acontrol microprocessor (542). Both microprocessors (540) and (542) maycomprise, for example, type 87C528 single-chip eight bitmicrocontrollers. The monitor microprocessor (540) is connected to aclock circuit (544) operating at approximately 14.7 KHz. The controlmicroprocessor (542) is connected to a clock circuit (546) operating atapproximately 3.6 KHz.

The monitor microprocessor drives a monitor data bus (548), labeled "MDBUS", and a monitor address bus (550), labeled "MA BUS". An addressdecoder latch (552) connected to the MD BUS (548) develops additionaladdressing signals on the MA BUS (550). Memory circuits in the form ofan EPROM (554) and RAM (556) are connected to both monitor buses (548)and (550).

A real time clock circuit (545) is connected to the MA BUS (550) and tothe monitor microprocessor (540) via a serial bus (551) labeled S BUSand EEPROM circuits (597) are connected between the MA BUS (550) and theS BUS (551).

Four latch circuits (558), (559), (560) and (561) are connected to theMD BUS (548). The first latch circuit (558) may be a type 74HC541 latchcircuit and is connected to the pump keyboard (26). The second latchcircuit (559) may be a type 74H273 latch circuit connected to thepatient LCD (36). The third latch circuit (560) may be a type 74HC541latch circuit connected to the program LCD (28). The LCD (28) providesan LCD ready signal to the monitor microprocessor (540) via a node B.The fourth latch circuit (561) is connected to an infrared circuit(562). The infrared circuit (562) includes a transmit circuit (564) andreceive circuit (566). The transmit circuit (564) includes an LED andconventional drive circuit for transmitting a carrier signal received ona line (565) from the monitor microprocessor (540) for remotecommunications. The receive circuit (566) receives infrared signals.

A further latch circuit (568) is connected to the MA BUS (550) forproviding enable signals to the patient LCD (36) and program LCD (28).

The control microprocessor (542) drives a control data bus (570),labeled CD BUS, and a control address bus (571), labeled CA BUS.Communications between the control microprocessor (542) and monitormicroprocessor (540) are implemented through a mailbox circuit (572)connected to the CD BUS (570) and MD BUS (548). The mailbox circuit(572) may comprise, for example, a type 74HC662 integrated circuit chipand associated logic circuits for implementing communication.Particularly, one of the microprocessors can send a message to the othermicroprocessor by sending the appropriate message to the mailbox circuit(572), where it will subsequently be read by the other of themicroprocessors.

A conventional analog to digital (A/D) converter, such as a type MAX153circuit, (574) is connected to the CD BUS (570) and CA BUS (571). TheA/D converter (574) is connected to an analog multiplexer (576) such asa type 74HC4051 multiplexer circuit which is also connected to the CABUS (571). The multiplexer (576) is connected to I/O devices asdiscussed below.

Additional latch circuits (578) and (580) are connected to the CD BUS(570) and CA BUS (571). The latch circuit (578) is connected to aplunger motor drive circuit (582). The latch circuit (580) is connectedto the valve motor drive circuit (584). The latch circuits (578) and(580) may comprise, for example, type 74HC564 integrated circuits. Thelatch circuits (578) and (580) are also connected to the monitor latchcircuit (561) for receiving an enable signal from the monitormicroprocessor (540), as discussed below.

Each of the plunger motor drive circuit (582) and valve motor drivecircuit (584) includes a conventional pulse width modulation (PWM)generator circuit for converting digital signals to a suitable pulsewidth modulated signal for driving the respective plunger motor (256)and valve motor (254), see FIG. 15. Particularly, the digital signalrepresents a duty cycle of motor input voltage on a zero to five voltscale. The operating frequency is approximately 68 KHz. Each PWMgenerator circuit in turn drives an H-bridge circuit for controllingvoltage to the plunger motor (256) and valve motor (254). A voltagesignal processing circuit (582-1) is connected to the plunger motordrive circuit (582) for detecting plunger motor voltage. A currentsignal processing circuit (582-2) is also connected to the plunger motordrive circuit (582) for detecting current drawn by the plunger motor(256). Similarly, a voltage signal processing circuit (584-1) isconnected to the valve motor drive circuit (584) for detecting valvemotor voltage. A current signal processing circuit (584-2) is alsoconnected to the valve motor drive circuit (584) for detecting currentdrawn by the valve motor (254). The processing circuits (582-1,582-2,584-1 and 584-2) condition the detected signals which are input to thecontrol microprocessor (542) via the multiplexer (576).

The pressure transducer (362), see FIG. 16, is connected via a pressuresignal processing circuit (585) to the multiplexer (576) for providinginput of sensed pressure. The ultrasonic air transducer (130) isconnected via a processing circuit (587) to the control microprocessor(542).

Power for the pump (10) is provided by a 9V battery (586) connected to apower supply circuit (588). The power supply circuit (558) includessuitable voltage regulator circuits for maintaining desired level ofpower to the control microprocessor (542) and monitor microprocessor(540) and other related circuits, as is well known. The battery (586)and power supply circuit (588) are also connected to the multiplexer(576) for feedback.

Because the pump (10) is powered solely by a battery (586), it isimportant that energy management schemes be used, as discussed above. Inaccordance with the invention, the microprocessors (540) and (542)include an idle mode and a power-down mode. In the idle mode, theprocessor puts itself to sleep while all of the on-chip peripherals stayactive. Instruction to invoke the idle mode is the last instructionexecuted in the normal operating mode before the idle mode is activated.In the power-down mode, the oscillator is stopped and the instruction toinvoke power-down is the last instruction executed. Each mode isterminated by an external interrupt received from a heartbeat circuit(590) connected to an oscillator (592). The processors (540) and (542)also wake themselves up from the idle mode by using internal timerinterrupts. The heartbeat circuit (590) is configured to provide a pulseor heartbeat signal every 7.8125 msec. Upon receiving the heartbeatsignal, each of the microprocessors (540) and (542) returns to thenormal operating mode.

A watchdog circuit (594) is connected to each of the microprocessors(540) and (542). The watchdog circuit (594), as described below,operates with a sequence that verifies that the monitor microprocessor(540) produces a "monitor OK" pulse and subsequently the controlmicroprocessor (542) produces a "control OK" pulse, then followed by a"monitor OK" pulse, etc., and that these pulses are at the correct timeintervals.

The watchdog circuit (594) is also connected to each of a control alarm(596) and monitor alarm (598). The control alarm (596) is connected tothe CD BUS (570). The monitor alarm (598) is connected to the MD BUS(548). The control alarm (596) provides a control alarm feedback signalto the monitor microprocessor (540). The monitor alarm (598) provides amonitor alarm feedback to the control microprocessor (542) via themultiplexer (576).

With reference to FIG. 33, an electrical schematic for the watchdogcircuit (594) is illustrated. The watchdog circuit (594) receives amonitor watchdog reset, or OK signal, labeled MONOK from the monitormicroprocessor (540), a control watchdog reset, or OK signal from thecontrol microprocessor (542), labeled CONOK, and a reset signal from thepower supply (588). Each of the CONOK and MONOK signals are connected toinputs of a negative OR (NOR) gate U69D. The MONOK signal is alsosupplied to one input of an AND gate U66D. The CONOK signal is alsoapplied to one input of an AND gate U66C. The output of the NOR gateU69D is the clock input of a flipflop U72A. The inverted output of theflipflop U72A is fed back to its dam input as well as the second inputof the AND gate U66C. The non-inverted output of the flipflop U72Acomprises the second input of the AND gate U66D. The output of the ANDgates U66C and U66D comprise inputs to a NOR gate U69C, the output ofwhich is connected to the clock input of a flipflop U72B. The data inputof the flipflop U72B is connected to a plus voltage failsafe input. Theinverted output of the flipflop U72B comprises a sequence OK signalcoupled to an inverted input of an AND gate U66B.

The watchdog circuit 594 also includes a timer circuit U73A in the formof a monostable multivibrator, such as a type MAX 690A integratedcircuit. The timer U73A, at a WDI input, receives a watchdog resetsignal from the output of the NOR gate U69D. An inverted RST output ofthe timer U73A is coupled to the second inverted input of the AND gateU66B.

The watchdog circuit (594) operates as a state machine having threestates--waiting for a MONOK signal, waiting for a CONOK signal andsequence violated. The circuit (594) alternates between the waitingstates unless the alternating sequence is violated or unless thealternating sequence did not begin with the MONOK signal. In that case,the circuit enters the sequence violated state.

The operation of the watchdog circuit (594) is as follows. As long asthe output of the AND gate U66B is high, then the microprocessors (540)and (542) are indicated to be operating properly. A watchdog trip occurseither if no OK signal is received within 3.2 seconds, or the OK signalsare out of sequence. Particularly, the OK sequence must alternatebetween the MONOK and the CONOK signal.

At startup, the inverted output of each flipflop U72A and U72B is highdue to reset. Similarly, the output of the timer circuit U73A is high,so that the output of the AND gate U66B is high. With the invertedoutput of the flipflop U72A high, the AND gate U66C is enabled. Becausethe non-inverted output of the flipflop U72A is low, the AND gate U66Dis disabled. The first pulse received should be the MONOK signal fromthe monitor microprocessor (540). Assuming the pulse is received, thepulse is applied to the second AND gate U66D, which has been disabled.The output of the NOR gate U69D clocks the flipflop U72A so that theoutputs alternate. This has the effect of enabling the AND gate U66D anddisabling the AND gate U66C. Assuming the next pulse received is theCONOK pulse, then the pulse is applied to the NOR gate U69D, which againclocks the flipflop U72A and is also applied to the disabled AND gateU66C. If consecutive pulses are received from the same processor, thensuch occurrence will be detected by one of the AND gates U66C or U66D.For example, if the AND gate U66C is enabled, indicating that the lastpulse received was the CONOK pulse, and another CONOK pulse is received,then the output of the AND gate U66C goes high, causing the NOR gateU69C to clock the flipflop U72B so that its inverted output goes low,causing the output of the AND gate U66B to go low to indicate a watchdogerror condition. Similarly, if two consecutive MONOK pulses arereceived, then the output of the AND gate U66D goes high to clock theflipflop U72B through the NOR gate U69C.

The watchdog circuit (594) otherwise detects a failure if no pulse isreceived every 3.2 seconds. Particularly, when either the MONOK or CONOKsignal pulses the NOR gate U69D, that pulse is used to reset the timercircuit U73A. If no pulse is received for 3.2 seconds from either theMONOK or CONOK inputs, then the timer U73D output to the AND gate U66Bgoes low, so that the DOGOUT output of the AND gate U66B goes low toindicate a watchdog failure. A watchdog failure results in a resetsignal being sent to the microprocessors (540) and (542). Also, awatchdog failure disables the plunger motor drive (582) and the valvemotor drive (584), via the respective latch circuits (578) and (580).Disabling the motors stops all pumping action, leaving one of the pumpchambers tube ends pinched.

L. System Peripherals

The ambulatory infusion pump (10) is part of a system illustrated inFIG. 39 which includes, in addition to the soft pump case (12), thesolution bag (64), the pump cassette (86) and the PCA switch (44), aremote communication interface unit (950), remote programmer (952) and aprinter (954).

The RCIU (950) consists of a telephone modem and an IR input/output(951). A block diagram of the RCIU is illustrated in FIG. 41. Withreference to FIG. 41, a block diagram illustrates a circuit for the RCIU(950), see FIG. 39. The RCIU is a telephone to modulated infraredtransceiver acting as an interface between a local pump (10) and remoteprogrammer (952), as illustrated in FIG. 39. Particularly, the pump (10)is adapted to receive infrared signals for remote programming. When theremote programmer (952) is physically remote, it cannot directlytransmit IR signals to the pump (10). In that instance, the programmer(952) transmits programming information over commercial phone lines tothe RCIU (950), which converts the information to infrared signals tothe pump (10), and vice versa.

The RCIU (950) includes a power supply circuit (980) for powering thevarious circuit components. A modem circuit (982) is connected to thetelephone line, as is a phone monitor circuit (984). The modem circuit(982) is connected to a tone detector (986) which provides an answertone detected signal to an RClU controller (984). The modem circuit(982) has a data line (988) connected to a switch matrix (990). Theswitch matrix (990) is also connected to an IR transceiver circuit (992)and to the RCIU controller (984). The RCIU controller is also connectedto a beeper (994).

The specific circuitry for the RCIU (950) is conventional in nature andtherefore is not described in detail herein. Particularly, the RCIUcontroller acts as a conventional modem to initiate or receive "phonecalls" to a remote programmer (952), see FIG. 39. Communication isestablished in a conventional manner. Once communication is established,then the RCIU controller (984) controls operation of the switch matrix(990) to receive data either over the phone line via the modem circuit(982) or via the IR transceiver circuit (992), converts the receiveddata to the other format, i.e., IR to modem or vice versa, and thentransmits the received data in the converted format via the oppositemedia from which it was received.

The remote programmer (952) includes a status LCD (956) and a programLCD (958). The program LCD (958) is identical to the program LCD (28) ofthe ambulatory infusion pump (10). The remote programmer also includes akeyboard (960) which is identical to the keyboard (30) of the ambulatoryinfusion pump (10). In addition, the remote programmer includes a numberof numeric entry controls (962) which simplify programming via theremote programmer. An IR input/output device (964) is provided forcommunication with the IR window (70) of the ambulatory infusion pump(10) and the IR input/outputs of the RCIU (950).

With reference to FIG. 34, a block diagram illustrates an electricalcircuit for the remote programmer (952). The circuit is essentially aduplicate of the circuit associated with the monitor microprocessor(540), see FIG. 32. Therefore, the circuit is not described in detailherein. For simplicity, like elements are indicated with like, primedreference numerals. Among the differences are the addition of aninternal modem circuit (541) connected to the monitor microprocessor(540'). The modem circuit (541) may include, for example, a type CH1782modem circuit module. Also, the patient LCD is replaced with the statusLCD (956). Both the status LCD (956) and program LCD (958) are connectedto the latch circuit (559'). Also, a conventional microprocessorwatchdog (594') is used.

The printer (954) is a standard printing device having an IRinput/output (966).

FIG. 39 illustrates remote programming use of the remote programmer(952) and the RCIU (950). Communication may be transmitted overcommercial phone line (966). The RCIU (950) is located in the immediatevicinity of the pump and is powered by an AC adaptor (970). An IR window(70) of the pump is maintained within approximately six inches of an IRinput/output (951) of the RCIU (950). The printer (966) may be linked toa second IR window (70A) of the pump (10). At the remote location, theremote programmer (952) is connected directly to the commercial phoneline (968). It is powered by an AC adaptor (972). A printer (954) havingan IR input/output (966) is maintained in infrared communication with anIR input/output (964) of the remote programmer (952). The programmer(952) can be used for direct wireless programming of the pump bypositioning the programmer with its IR input/output (964) in direct IRcommunication with the IR window (970) of the pump (10) and programmingand access to pump data can be conducted in the manner discussed belowin Section M4 with respect to FIG. 35D.

M. Monitor Microprocessor Software

As set forth above, the ambulatory infusion pump includes a monitormicroprocessor (540) and a control microprocessor (542). The monitormicroprocessor and its software generally supports programming, userinterface, communication and peripheral hardware with execution of thepumping sequence by the control microprocessor. The flow diagram of FIG.35A comprises a generalized flow diagram representing the main routineof the monitor microprocessor software. FIGS. 35B-D representsub-routines called by the monitor microprocessor main routine.

1. Main Monitor Routine

The monitor microprocessor main routine begins at block (620), whichrepresents a user powering on the pump, at which time initialization ofthe monitor main routine and self-test routines are performed. Theself-tests includes RAM test, ROM test, integrity of delivered program,communication between the control and monitor microprocessors and testof the pump beeper and visual alarms. Block (622) represents a routinefor supporting the programmer display and the programmer controls. Adetailed flow diagram of block (622) is provided in FIG. 35B. Supportsfor the patient display and the patient controls is provided at block(624). This includes drawing of the patient display such as thatillustrated in FIG. 26 and support for the on/off control (38) and thebolus dose control (40) shown in FIG. 25. At block (626) support isprovided for the beeper and patient LED which provide both indication ofnormal pump operation and, under circumstances described below, errornotification. Communication with the control microprocessor is conductedat block (628) which shown in greater detail in the flow diagram of FIG.35C.

At block (630) the routine determines whether or not the pump iscurrently delivering a therapy. If not, printer support is provided atblock (632). The printer support controls printing of historical dataand other operating parameters. Communication with the remote programmeris supported at block (634). A detailed flow diagram of the substantivecontrolling communication support with the remote programmer iscontained in FIG. 35D. The monitor microprocessor is put to sleep at(636). The monitor microprocessor remains asleep until block (638),whereat the next heartbeat awakens the monitor microprocessor and themain routine continues.

Returning to decision block (630), if the pump is delivering a therapy,decision block (640) is reached and a determination is made whether theprogram entered at block (622) has been mapped by the monitormicroprocessor. If it has not, the program is mapped at block (642). Atblock (642), the monitor microprocessor generates two program maps: amonitor program map and a control program map. The monitor program mapcontains a series of operations necessary to administer the deliveryprofile entered at block (622) in the manner described with reference toFIG. 35B. Following compilation of the monitor and control program maps,the monitor program map is executed at block (644). Of course, if theprogram maps have already been compiled, block (644) is reached directlyfollowing decision block (640). If the monitor program map requiresactuation of the pump mechanics, an appropriate command is generated andflagged at block (644). The flag is subsequently detected at block (628)and communication with the control microprocessor is conducted in themanner discussed with reference to FIG. 35C. In a like manner, if acontrol program map is constructed in block (642), it is flagged andcommunicated to the control microprocessor at block (628).

2. Support Programmer display and Controls Routine

With reference to FIG. 35B, a flow diagram illustrates the supportprogrammer display and programmer controls of block (622). In describingthe support programmer display and programmer control, typicalprogramming sequences are discussed. It should be noted, however, thatat those blocks described below where the user is assumed to have takenaction, such as block (654) where the user positions the cursor with the"up" and "down" keys, the user may instead press the "cancel" button,thus returning to the previously selected mode screen or the user may donothing at all, essentially leaving the pump in limbo.

At block (648) the current mode screen is drawn, such as the"intermittent with bolus" mode screen shown in FIG. 29. As discussedwith reference to FIG. 27, five delivery modes (517) are available:"continuous", "continuous with PCA", "continuous with taper","intermittent" and "intermittent with bolus". These delivery modes arediscussed in greater detail in Section H above with reference to FIG.37A-F.

At decision block (650) determination is made whether or not a user hasdepressed the "change mode" button (526). If the "change mode" button(526) has been pressed, SELECT DELIVERY MODE screen illustrated at FIG.27 is drawn at block (652). At block (654), the user positions thecursor with the up and down keys (522) to highlight with the cursor theintended delivery mode. The user presses the "select" button (523) atblock (656) when the desired delivery mode has been highlighted by thecursor. The mode screen for the selected mode is then drawn at block(658), following which the main routine is resumed.

If at decision block (650) the "change mode" button (526) has not beenpressed, at block (660) the routine determines whether the "edit/view"button (525) has been pressed. Pressing of the "edit/view" button allowsthe user to enter new parameters for the selected delivery mode. Atblock (662) the "setup" screen is drawn for the selected delivery mode.A sample "setup" screen is illustrated at FIG. 28. At block (664) theuser positions the cursor with the "up" and "down" keys (522) for thepurpose of entering or altering one of the input options (521).

The program includes a lockout feature to prevent unauthorized orinadvertent alteration of selected input options. A clinician canprevent alteration of selected input options without input of a selectedpassword or code where restricted access to an input option is necessaryfor patient safety. The feature is controlled by a clinician entering aselected lock level which tells the program whether a particular inputoption can be altered. If the input option can be altered, the inputoption line, including the input valves, is highlighted when the cursoris positioned at the particular input option. This highlighting is knownas a "regular cursor" and is illustrated at (665) of FIG. 28. If theinput option cannot be altered, only a vertical line or "edge cursor" tothe immediate left of the input option will be highlighted when thecursor is positioned at that particular input option, as illustrated at(665A) of FIG. 28.

At decision block (666) the routine determines whether the user is inlock level "0", which allows unrestricted access. If the user is in locklevel "0", the regular cursor is drawn at block (668). If the user isnot in lock level "0", at decision block (669) the routine determineswhether the new cursor position or input option is lock level protected.If it is not, at block (668) the regular cursor is produced. If thecursor position or input option is lock level protected, at block (670)the edge cursor is produced.

Returning to block (668), if the regular cursor is produced at block(672), the routine inquires whether the user has pressed the "select"key (523). If not, the user may reposition the cursor with the "up" and"down" keys (522) at block (664). If the user has pressed the "select"key (523), the user may then modify the input value parameter with the"up" and "down" keys (522) at block (674). When a desired value isarrived at block (674), the user presses the "select" key (523) at(676). The routine then simultaneously "deselects" the input optionretracting the cursor, and "enters" the modified value. Block (678)represents three user options. The user may return to block (664) andreposition the cursor with the "up" and "down" keys (522). Or, the usermay press the "cancel" key (527), block (679), deleting the new program.The previous "mode" screen will then be drawn at block (680) with theinput option values unchanged. The main routine is then rejoined atblock (624). The third option shown at block (682) is for the user topress "finished program". The new "mode" screen with the newly selectedvalues is then drawn at (684). The main routine is then rejoined atblock (624).

3. Support Communication with Control Microprocessor Routine

FIG. 35C is a flow diagram illustrating in detail block (628) of FIG.35A, "support communication with control microprocessor". Communicationbegins at control block (688), where the routine determines whether aflag or flags have been raised at the "execute monitor program map"block (644) or the "program map" block (642) of the main monitorroutine, FIG. 35A. If such a flag has been raised, then the highestpriority message will be found at block (690). At decision block (692)determination is made whether the message to be sent requires movementof either the plunger motor or the valve motor. If the answer is yes,the appropriate motor is enabled at block (694). At block (696), themessage is then sent to the control microprocessor. At block (698), themessage family number is stored. The family number will subsequently becompared with a continuing message conveyed by the controlmicroprocessor as discussed below.

If at decision block (688) there is no message to be sent, at decisionblock (700) the routine determines whether any message is waiting fromthe control microprocessor. If no message is waiting, the main monitormicroprocessor routine simply continues. If a message is waiting fromthe control microprocessor, the message is picked up at block (702). Atdecision block (704) it is determined whether the message picked upmatches the message saved at block (698). If the message does not match,an alarm is produced at block (706). Whether the motor had been enabledand whether the picked up message relates to the motor is determined atblock (728). If the answer to both questions is yes, the motor isdisabled at block (710) and the subroutine returns to the main routine.If the answer is no, the subroutine returns directly to the mainroutine.

4. Support Communication with Remote Programmer Routine

FIG. 35D is a flow diagram illustrating the "support communication withthe remote programmer" subroutine of block (634) of the main monitorroutine. Those steps being performed by the remote programmer (952) areshown in solid lines, and those being performed by the monitormicroprocessor are shown in dotted lines. Communication between theremote programmer and the pump is conducted in one of three waysdetailed in Section L above: 1) directly by infrared linkage; 2) throughthe remote communication interface unit (RCIU); or 3) by linkage to theremote programmer through a local RCIU, an RCIU at the remote programmerlocation and phone lines. At decision block (714) the murine determineswhether the user has pressed the "Read Pump" key (964) of the remoteprogrammer. If not, at decision block (716) determination is madewhether the user has pressed the "Program Pump" key (966). If the answeris no, the murine returns to the main monitor routine and the monitormicroprocessor is put to sleep at block (636) (see FIG. 35A).

If at decision block (714) the user has pressed the "Read Pump" key(964), the remote programmer sends protocol bytes to the pump at (718).The protocol bytes include, for example, the respective serial numbersof the pump and remote programmer. At block (720), the monitormicroprocessor puts the current program, delivery history and previousforty-eight hour record into a buffer. At block (722), the monitormicroprocessor appends the protocol bytes and CRC 16 to the buffer. Atblock (724), the buffer is sent by the monitor microprocessor to theremote programmer. At block (726), the remote programmer echoes thebuffer to the remote microprocessor. At decision block (728), themonitor microprocessor determines whether the buffer echoed at box (726)matches the buffer sent to the remote programmer at box (724). If theanswer is yes, the communication is a success and the monitormicroprocessor continues the main routine at block (636) of FIG. 35A. Ifthe echo does not match the buffer, at block (730) the pump monitormicroprocessor sends the buffer back to the remote programmer. Atdecision block (732) the remote programmer determines whether thetransfer has been attempted a select number, or n times. If it has andthe echo fails to match the buffer sent by the monitor microprocessor ofthe pump, there is a communication failure and an alarm is sounded. Ifat decision block (732) the remote programmer microprocessor determinesthe transfer has not been attempted n times, the routine returns toblock (718) and is repeated until the echo matches the buffer ortransfer has been attempted unsuccessfully n times.

If the user has pressed the "Program Pump" key (966) at decision block(716), the remote programmer puts the current programmer in a buffer. Atblock (736), the buffer is appended with the protocol bytes (e.g., pumpand programmer serial numbers) and CRC-16. At block (738), the buffer issent to the pump. At box (740), the pump monitor microprocessor echoesthe buffer to the remote programmer. At decision block (742), the remoteprogrammer determines whether the echo matches the buffer sent to thepump. If the answer is yes, the communication is a success, and the mainroutine of the monitor microprocessor is continued, with the new programbeing implemented in the same manner as if the program had been entereddirectly at the pump. If the echo does not match the buffer, at decisionblock (744) the determination is made whether the transfer has beenattempted a select number or n times. If it has not, the routinecontinues at box (734) and repeats itself until the echo does match thebuffer or the transfer has been attempted a n number of times, at whichtime communication is a failure and an alarm is sounded.

N. Control Microprocessor Software

FIG. 36A is generalized flow diagram representing the major operationalroutine of the control microprocessor (542). The primary function of thecontrol microprocessor (542) is to execute the plunger and valve motioncontrol algorithms which are intended to provide variety of deliveryprofiles within acceptable predefined accuracy standards whileminimizing energy consumption and further while continuously monitoringthe pump mechanics to provide prompt notification of any failureconditions. FIGS. 36B-I are flow diagrams of subroutines called by themain control routine.

1. Main Control Routine

The main control routine begins at block (750) of FIG. 36A, wherein themain control microprocessor program is initialized. At decision block(752) it is determined whether the program map complied by the monitormicroprocessor (540) at block (642) of FIG. 35A has been received fromthe monitor microprocessor through execution of the supportcommunication with control microprocessor block (628) of FIG. 35A. If aprogram map has not been received from the monitor microprocessor, atdecision block (754) it is determined whether a delivery command hasbeen received from the monitor microprocessor. If a delivery command hasbeen received, at block (756) an error message is generated because asystem error has occurred if a delivery command is received by thecontrol microprocessor without having first received a program map. Theerror message generated at block (756), like all error messagesdiscussed in FIGS. 36A-I, is sent to monitor microprocessor (540), whichactivates an appropriate alarm. The control microprocessor verifies theactivation of an appropriate alarm by the monitor microprocessor. If thecontrol microprocessor is unable to verify that the appropriate alarmhas been activated, the control microprocessor will directly activate analarm. If at block (754) a delivery command is not received from themonitor microprocessor, the control microprocessor is put to sleep atblock (758) and at block (760) the control microprocessor is awakened bythe next heartbeat and decision block (752) is again entered.

If at decision block (752) a program map has been received from themonitor microprocessor (540), the program map is compiled at block (762)to set forth checking or verification parameters and further todetermine which of the five pump operation modes is required to fullyexecute the program map. A determination is made at decision block (764)whether a delivery command has been received from the monitormicroprocessor. If no delivery command has been received, the controlmicroprocessor (542) is put to sleep at block (766) until it is awakenedat the next heartbeat at block (768) and the control microprocessor thenagain executes decision block (764).

If a delivery command has been received from the monitor microprocessor,at decision block (770) it is determined whether the delivery commandwas expected. If a delivery command was received and was not expected,an error message is generated and conveyed to the monitor microprocessor(540). If the delivery command was expected at decision block (770), adelivery is executed at block (772). Delivery commands from the monitormicroprocessor only specify whether the infusion is to be 5, 25 or 125microliters. The delivery at block (772) is conducted in accordance withthe mode selection configured at block (762) to satisfy the deliveryprofile. Delivery is executed through one of five delivery routineswhich are discussed in greater detail with reference to FIGS. 37B-F.Inquiry is made at decision block (773) whether the delivery task hasbeen successfully completed. If the action has been successfullycompleted, at block (774) the volume remaining in the reservoir isupdated and the acceptability of the flow rate is confirmed. That is,when a select volume of liquid has been delivered, the routinedetermines if the time to deliver the select volume provides anacceptable flow rate. If the flow rate is acceptable, the routine isreset. At block (775) successful completion of the delivery sequence isreported to the monitor microprocessor. Although not illustrated in FIG.36A, if the timing check performed at block (774) does not confirmproper operation of the pump, an error message is sent to the monitormicroprocessor (540).

Returning to decision block (773), if a pumping action has not beensuccessfully completed, at block (776) fault recovery is attempted. Thefault recovery routine is shown in detail in FIG. 36I and will bediscussed below. At decision block (777) the routine determines whetherthe recovery was successful. If the recovery was successful, the routinecontinues at block (774). If the recovery was not successful, an errormessage is generated at block (778) and conveyed to the monitormicroprocessor (540). Continuing with block (775), following report of asuccessful delivery action to the monitor microprocessor (540), thecontrol microprocessor (542) is put to sleep at block (779) until thenext heartbeat at (780), wherein the control microprocessor (542) isawakened and the main routine returns to decision block (764).

As discussed above with reference to blocks (762) and (772), the maincontrol routine includes five subroutines, FIGS. 36B-F, for executingpump modes 1-5. The subroutines actuate the plunger and valve motors soas to discharge the desired volume of medication at the desired rate forthe desired time period. An overview of modes 1-5 is contained in FIG.38. Many of the details set forth in FIG. 38 will be apparent followingdiscussion of FIGS. 36B-F below. For the present purpose, it is onlynecessary to know that mode 1 delivers fluid at a rate of between0.1-0.4 ml/hr.; mode 2 delivers liquid at a rate of 0.5-7.9 ml/hr.; mode3 delivers medication at a rate of 8-49.9 ml/hr.; mode 4 deliversmedication at a rate of 50-249 ml/hr.; and mode 5 delivers medication ata rate of 250-390 ml/hr. Determination is made which one of modes 1-5 isexecuted at the "do delivery" block (772) in accordance with theselected delivery profile delivered to the control microprocessor as thecontrol program map. See FIG. 36A, block (752,762).

2. Mode "1" Delivery Routine

FIG. 36B is a flow diagram illustrating a routine for executing mode 1delivery. At decision block (785) it is determined whether the plungeris at position "-1". If it is, at block (786) the plunger motor (256) isadvanced one revolution. Thus, block (785-786) constitute a refillcondensation sequence which ensures that when the plunger (120) is atposition "0", the pump chamber (140) is at the expected volume. If theplunger position is not equal to "-1" at block (785) or followingadvancement of the plunger one motor revolution at (786), at decisionblock (787) it is determined if the plunger is at position "0". If theplunger is at position "0", the plunger motor is advanced three motorrevolutions to advance the plunger to position "3" at block (788).Advancing the plunger three motor revolutions at block (788) negates anytolerance stacking between the position of the plunger and the platen,and thereby improves pump accuracy. At block (789) the proximal or inletvalve (122) is closed. Next, at block (790) a fill and valve leak testsequence is executed. A flow diagram of block (790) is shown in FIG. 36Gand is discussed below. Following execution of the fill and leak testsequence (790), at block (792) the stroke target is set to position"13". "13" is the preferred target position so that the pump chamber iscompressed only a total of thirteen revolutions to prevent the pumpchamber from acquiring a "memory" of less than the full refill volume asa result of occupying a compressed position for extended periods oftime. At block (793) the distal or outlet valve (124) is opened. If atdecision block (787) the plunger position is not equal to "0", theroutine continues at block (793) with the opening of the distal valve.At block (794) the plunger is advanced one motor revolution to deliverfive microliters of medication. Concurrently, the pressure within thepump chamber (140) is measured by the pressure transducer (362) for thepurpose of detecting a downstream occlusion by comparison of the readpressure with a predetermined reference pressure. If the predeterminedreference pressure is exceed, a downstream occlusion error message isgenerated by the control microprocessor and conveyed to the monitormicroprocessor. If no downstream occlusion is detected, at block (795)the distal valve (124) is closed. If it is, at decision block (796) itis determined whether the pump chamber pressure is greater than or equalto three psi above the inlet line pressure. If it is, at block (797) thestroke target position is set to "25". The stroke target position is setto "25" at block (797) in order to ensure that the pump chamber will besubject to sufficient compression during the pumping sequence togenerate a pump chamber pressure greater than the reference pressure soas to ensure any downstream occlusion is detected. If at block (796) thepump chamber pressure is less than three psi above the inlet linepressure, or following setting of the stroke target to "25" at block(797), at decision block (798) the routine determines whether theplunger has attained the stroke target position. If so, at block (800)the inlet or proximal valve (122) is opened. At (82) the plunger is thenretracted by reverse rotation of the plunger motor to position "-1".Also at block (802), at each revolution of the plunger motor theultrasonic air detect (130) transmitter produces an ultrasonic signalwhich is received by the air detect receiver. This procedure isdiscussed above in Section F. The receiver then transmits a signal tocontrol microprocessor (542), the amplitude of which indicates whetheran air or liquid is present in the tube segment between the transmitterand receiver. More particularly, the ultrasonic air detect takes a snapshot of a tube segment between the transmitter and receiver of theultrasonic air detect (130) containing on the order of 25 microliters ofliquid each revolution of the plunger motor. If the amplitude of thesignal received from the ultrasonic air detect indicates that greaterthan 50% of the volume of the tube segment is filled with air, themicroprocessor stores an "air in tube" signal. As the plunger motorcompletes the next revolution, a new 5 microliters is introduced intothe tube segment as 5 microliters leaves the tube segment and anotherpulse is transmitted by the transmitter. If the amplitude of the signaldictates, the microprocessor stores an "air in tube" signal. At decisionblock (803) the routine determines if the sum of the "air in tube"signals exceeds a select number for any two consecutive refill cycles.The select number is preferably 15. If the select number is exceeded,pump operation is halted and an error message is generated at block(804). If the select number is not exceeded, the routine returns toblock (773) of FIG. 36A. Likewise, if at block (798) it is determinedthat the plunger is not at the stroke target position, the routinereturns to block (773) of FIG. 36A.

3. Mode "2" Delivery Routine

The routine for executing delivery mode (2) is illustrated in the flowdiagram of FIG. 36C. At decision block (810) the routine determineswhether the plunger is in position "-1". If the plunger is in position"-1", the plunger is advanced one motor revolution to position "0" atblock (811), the "refill compensation sequence" discussed above withreference to blocks (785-786) of FIG. 36B. If the plunger is not inposition "-1", or following block (811) at decision block (812) it isdetermined whether the plunger is in position "0". If the plunger is inposition "0", at block (813) the plunger motor is advanced threerevolutions, thereby advancing the plunger to position "3", as discussedabove with respect to block (788) of FIG. 36B. At block (814) theproximal or inlet valve (122) is closed. Next, at block (815) the fillvalve and leak test sequence is executed. A flow diagram of block (815)is shown in FIG. 36G, and is discussed below. Following execution of thefill valve and leak test sequence at block (815), at block (816) theoutlet or distal valve (124) is opened. At block (817) the stroke targetis set to "13" and the routine continues at block (818) in the samemanner as if the plunger position had not been equal to "0" at decisionblock (812). At block (818) the plunger motor is advanced one revolutionto deliver five microliters of medication. Concurrently, pressure withinthe pump chamber (140) is measured by the pressure transducer (362) forthe purpose of detecting a downstream occlusion. The pressure within thepump chamber (140) is compared with a predetermined reference pressure.If the predetermined reference pressure is exceeded, an error message isgenerated. If the predetermined reference pressure is not exceeded, theroutine continues at decision block (819). At decision block (819) it isdetermined whether the pump chamber pressure is grater than or equal tothree psi above the inlet line pressure which is determined during thevalve test sequence at block (815) and is designated in FIG. 36G as (A).If it is, the stroke target position is set to "25" at box (820) for thereasons set forth above with respect to block (797) of FIG. 36B. If thepump chamber pressure is found not to be greater than or equal to threepsi above the inlet line pressure at decision block (819), or followingsetting of the target stroke position at block (820), it is determinedwhether the plunger is at the stroke target position. If it is, at block(823) the outlet or distal valve (124) is closed. Thereafter, at block(824) the inlet or proxima valve (122) is opened. At block (825) theplunger motor is reversed and the plunger is retracted to position "-1"while the ultrasonic air detect (130) is actuated after each plungermotor revolution. At decision block (826) the routine determines whetherexcessive air has been detected in the incoming fluid as discussed abovewith reference to block (803) of FIG. 36B and, if so, an error messageis generated at block (827). If the amount of air in the fluid is notexcessive, the routine returns to block (773) of the main controlroutine illustrated in FIG. 36A. Likewise, if at decision block (822)the plunger position is not equal to the stroke target, the routinereturns to block (773) of FIG. 36A.

4. Mode "3" Delivery Routine

FIG. 36D illustrates the subroutine for executing delivery mode three.Determination is made at decision block (840) whether the plungerposition is equal to "-1". If the plunger position is equal to "-1", theplunger is advanced one motor revolution at block (842). At block (844)the proximal or inlet valve is closed. If the plunger position is notequal to "-1" at block (840), or following closure of the proximal valveat block (844), at decision block (846) it is determined whether theplunger position is equal to "0". If the answer is yes, the fill andvalve leak test sequence described in detail with respect to FIG. 36G isperformed at block (848). Thereafter, at block (850) the distal oroutlet valve is opened. If the plunger position is not equal to "0", orfollowing opening of the distal valve at block (850), at block (852) theplunger motor is advanced five motor revolutions at 2000 rpm nominalspeed so as to discharge twenty-five microliters of medication. At theend of each motor revolution, except during the acceleration period, thepump chamber pressure is monitored to check for downstream occlusions.At decision block (854) it is determined whether the plunger (120) is atposition number "25". If it is not, the routine returns to block (774)of FIG. 36A. If the plunger position is equal to "25", at block (856)the distal or outlet valve (124) is closed and the proximal or inletvalve (122) is opened. At block (858) the plunger (120) is retracted 26motor revolutions at a 2000 rpm nominal speed. At the conclusion of eachrevolution of the plunger motor (256), excluding the accelerationperiod, ultrasonic air detection takes place. At decision block (860) itis determined whether too much air has entered the pump chamber. If so,an error message is generated at block (862). If the amount of air isacceptable, the routine returns to block (773) of FIG. 36A.

5. Mode "4" Delivery Routine

FIG. 36E illustrates the routine for executing delivery mode four.Determination is made at decision block (866) whether the plunger is atposition "-1". If it is, the plunger is advanced one motor revolution atblock (868) and the outlet valve (124) is closed at block (870). If theplunger position was not equal to "-1" at decision block (866), orfollowing execution of block (870), at block (872) fill and valve leaktest sequence described below with reference to FIG. 36G is conducted.At block (874) the distal valve is opened. At block (876) the plunger isadvanced to position "25" at a nominal speed of 4000 rpm, delivering 125microliters of medication. Pump chamber pressure is read at the end ofeach revolution, excluding the acceleration period, to test fordownstream occlusions. If a downstream occlusion is detected, an alarmsignal is generated. At block (878) the outlet valve is closed and theinlet valve (122) is opened. At block (880) the plunger (120) isretracted 26 motor revolutions at a nominal speed of 4000 rpms. At theend of each revolution of the plunger motor (256), excluding theacceleration period, the ultrasonic air detect (130) detects any air inthe fluid entering the pump chamber (140). At decision block (882) it isdetermined whether too much air has entered the pump chamber. If excessair has entered the pump chamber, an error message is generated at block(883). If the amount of air is acceptable, the routine returns to block(773) of FIG. 36A.

6. Mode "5" Delivery Routine

FIG. 36F is a flow diagram illustrating execution of delivery mode 5. Itis determined at decision block (866) whether the plunger (120) is inposition "-1". If the plunger is in position "-1", the plunger isadvanced one motor revolution of plunger motor (256) at block (888). Atblock (890) the inlet valve (122) is closed. The fill and valve leaktest sequence described in detail with reference to FIG. 36G isperformed at block (892). Block (894) and block (896) are then performedin parallel. More particularly, at block (894) the plunger motor (256)is accelerated to 4000 rpm nominal speed. The plunger motor revolutionsare monitored by means of the Hall sensor (400) on the plunger motor(256). Concurrently, at block (896) the outlet valve (124) is opened soas to discharge fluid from the pump chamber (140). Upon opening of theoutlet valve (124) at block (896), at block (898) the plunger motor(256) is advanced to position "24" at 4000 rpm nominal speed. Pressureis checked after each motor revolution 2 for downstream occlusion. Block(898) and (900) are then performed in parallel. More particularly, atblock (898) the plunger motor is slowed to 2000 rpm for its 25threvolution. When this revolution is complete, the plunger motor isstopped by the magnetic detent following 90 degrees of additionalrotation and a final occlusion pressure check is conducted.Concurrently, at block (900) the outlet valve (124) is closed and theinlet valve (122) is opened. Upon closure of the outlet valve (124), atblock (902) the plunger motor (256) is accelerated backward to 4000 rpm,with the revolutions being counted by monitoring of the Hall sensor(400). At block (904) the plunger motor (256) operates at 4000 rpm untilthe plunger (120) is in position "1", at which time the plunger motor isslowed to 2000 rpm and is brought to rest at position "0" in the sameway it is advanced at block (898). Ultrasonic air detection occurs aftereach revolution, excluding acceleration and deceleration. The results ofthe ultrasonic air detect are evaluated at block (906). If excessive airis detected, an error message is generated at block (907). If the amountof air is acceptable, the routine returns to block (773) of FIG. 36A.

7. Fill and Valve Leak Test Sequence Routine

The "fill and valve leak test sequence" routine described in eachdelivery mode subroutine of FIGS. 36B-F is illustrated in the flowdiagram of FIG. 36G. At block (910) the inlet line pressure designatedherein as "A" is read using the pressure transducer (362). The inlet orproximal valve (122) is then closed at block (911). Following a shortdelay at block (912), the pump chamber pressure is read again at block(913) and is designated herein as "B". At block (914) a delay occurswhich is a function of the rate of delivery at the particular mode. Thatis, the higher the rate of delivery, the shorter the delay at block(914). At block (915) the pump chamber pressure is read again and isdesignated herein as "C". At block (916) it is determined whetherpressure "C" exceeds pressure "B" by more than a select amount. That is,at decision block (916) it is determined whether the inlet pincher valve(122) is leaking, which may be the case where the inlet line pressure"A" exceeds the pump chamber pressures "B". If pressure "C" exceedspressure "B" by more than the select amount, an error message isgenerated at block (917). If it does not, at block (918) the plunger(120) is advanced three revolutions of the plunger motor (256). At block(919) the pump chamber pressure is again read and the read pressure isdesignated herein as "D". At decision block (920) it is determinedwhether pressure "D" exceeds pressure "C" more than a select amount. Ifpressure "D" does not exceed pressure "C" more than a select amount,this is an indication that one of the inlet or outlet pincher valves(122,124) is leaking. The test is then repeated at block (921), wherethe plunger (120) is advanced three more revolutions of the pump motor.At (922) the pump chamber pressure is again read, and designated "E"herein. At decision block (923) it is determined whether pressure "E"exceeds pressure "D" more than a select amount. If it does not, thisconfirms a leak at one of the inlet and outlet pincher valves (122,124)and an error message is generated at block (924). If "E" does exceed "D"by more than a select amount, at block (925) a delay is instituted.Likewise, if at decision block (920) it is determined that pressure "D"does exceed pressure "C" by more than a select amount, at block (926) adelay is instituted. Following the delays at blocks (925), (926), at(927) the pump chamber is again read and designated herein as "F". Atdecision block (928) it is determined whether pressure "D" (or, if atdecision block (920) "D" does not exceed "C" by more than a selectamount, pressure "E") exceeds "F" by more than a select amount. If itdoes, this again indicates that one of the inlet or outlet pinchervalves (122,124) is leaking, and an error message is generated at block(929). If it does not, at block (930) it is determined whether theroutine is in delivery mode "4" or "5". If it is not, at block (931) theplunger motor is retracted to the start position. Following retractionof the plunger at block (931), the routine returns to block (792), (816)or (850) of delivery modes 1-3 illustrated in FIGS. 36B-36D,respectively. If at decision block (930) the routine is in delivery mode4 or 5, the routine returns to block (874) or block (894) of FIGS. 36Eand 37F, respectively.

8. Sleep Routine

Between each of the blocks of the routines illustrated in FIGS. 36B-F isinterposed an electronic sleep feature which, in conjunction with aheartbeat generator (590), see FIG. 31, minimizes power consumption bycausing the control microprocessor (542) to power down when no controlactivity is required. The operation of the electronic sleep feature isillustrated in FIG. 36H. At decision block (810) it is determinedwhether a motion control activity is required. A motion control activityis required when a change in an output related to motion control must bemade. If a motion control activity is required, the motion controlactivity is initiated at block (812). If no motion control activity isrequired, or after a motion control activity is completed at block(812), at block (814) determination is made whether the next activity isdue to be initiated the next heartbeat. If the activity is not due tohappen before the next heartbeat, then the control microprocessor (542)is put to sleep. At block (818) the next heartbeat is detected and theroutine returns to decision block (810). If it is determined at decisionblock (814) that the next activity is due to happen before the nextheartbeat, an internal timer for when the next activity is due to happenis set at block (820). The control microprocessor (542) then goes intoan idle state or a "half asleep state" at block (822) and at block (824)waits for the timer period to expire. Upon expiration of the timerperiod, the routine returns to block (812) where the motion controlactivity is completed.

9. Fault Recovery Routine

The software fault recovery attempts routine, which is called at theblock (776) of the main control microprocessor routine illustrated inFIG. 36A, is illustrated in the flow diagram of FIGS. 36I-36L.

Unexpected operating conditions will cause error flags to be set. Withinthe dual microprocessor software system, detection of fault conditionscauses recovery attempts to be made within the constraints of thesystem. This improves fault tolerance of the pump (10) which in turnimproves performance characteristics as it attempts to overcometransient fault conditions such as a patient rolling over on the tubingor a patient pressing against an IV bag.

Referring initially to FIG. 36I, a flow diagram illustrates the faultrecovery routine. The routine begins at a decision block (936) whichdetermines whether the error detected at the decision block (773) of themain control microprocessor routine of FIG. 36A is a recoverable error.

Non-recoverable errors include an absence of a plunger home signal,absence of a valve neutral signal, a feedback circuitry error, and anillegal pump command (e.g., a command disrupted during transmission fromthe monitor microprocessor to the control microprocessor). If such anon-recoverable error is identified at decision block (936), at block(937) an error message is generated and conveyed to the monitormicroprocessor (540). At block (944) the routine returns to block (777)of the main control microprocessor subroutine of FIG. 36A.

If the error is not identified as a non-recoverable error, the routinecontinues at decision block (938) where it is determined whether theerror message is that a distal occlusion condition is present. If adistal occlusion occurs as determined by an excessive pressure rise,then a recovery murine illustrated in FIG. 36J is implemented. Thisroutine begins at a block (1000) by closing the distal or outlet valve(124), opening the proximal or inlet valve (122) and retracting theplunger (120). A decision block (1002) then determines if eitherdelivery mode 4 or 5 was being executed. If not, then an error messageis generated at a block (1004) and the routine ends at a block (1006).If either delivery mode 4 or 5 was being executed, then the originalcommand being acted upon at the time the error occurred is reexecuted ata block (1008). A decision block (1010) determines if the command wasreexecuted successfully. If not, then control proceeds to the block(1004). If the command was successful, then a recovery count isincremented at a block (1012) and the routine ends.

The recovery count is used to determine if excessive recovery operationshave occurred. If too many recovery operations have occurred, then thedelivery action could be impacted negatively, warranting shutting downthe pump (10) and generating an alarm.

In the flow diagrams, when the recovery count is incremented it isassumed that recovery is successful. This determination is used at thedecision block (777) of FIG. 36A. If, instead, an error message isgenerated, then it is assumed that recovery was unsuccessful and furtheroperation of the pump driving mechanism is halted.

Returning to FIG. 36I, if the error message is not for a distalocclusion, as determined at the decision block (938), then a decisionblock (940) determines if the error message is for a bad refill of thepump chamber. This occurs when there is an insufficient indicatedpressure rise after advancing the plunger (120) with both valves (122)and (124) closed. If a bad refill error has occurred, then controladvances to a block (941) to implement a recovery routine illustrated inFIG. 36K.

The bad refill recovery routine begins at a block (1014) which opens theproximal valve (122). The plunger (120) is retracted at a block (1016)to a compensated position. A decision block (1018) determines if thecommands generated at the block (1014) and (1016) were executedsuccessfully. If not, then an error message is generated at a block(1020) and the routine ends at a block (1022). If the commands weresuccessful, then a two second delay is implemented at a block (1024) andthe original delivery command is reexecuted at a block (1026). Adecision block (1028) determines if the original command was reexecutedsuccessfully. If not, then control proceeds to the block (120). If so,then the recovery count is incremented at a block (1030) and the routineends.

Returning to the flow diagram of FIG. 36I, if the error message was notfor a bad refill, as determined at the decision block (940), then adecision block (942) determines if the error was for a valve closurefault. This fault occurs if there is an increase in indicated pressureafter closing the proximal valve (122) and delaying for a flow ratedependent period of time. If so, then a recovery routine illustrated inFIG. 36L is implemented at a block (943).

The valve closure fault recovery routine begins at a block (1032) whichrepositions the mechanism to a "home" position. More particularly, theplunger (120) is returned to its "home" or "zero" position, the distalvalve (124) is opened and the proximal valve (122) is closed. Before themechanism returns to the "home" position, however, each of the inletvalve (122), outlet valve (124) and plunger (120) are tested byactuation to assure they are functioning properly. If they are not, orif the mechanism cannot return to the "home" position, as determined ata decision block (1034), then an error message is generated at a block(1036) and the routine ends at a block (1038). If the repositioning issuccessful, then a two second delay is implemented at a block (1040).The original command is then reexecuted at a block (142). A decisionblock (1044) then determines if the original command was reexecutedsuccessfully. If not, then control proceeds to the block (136). If so,then the recovery count is incremented at block (1046) and the routineends.

Returning to the flow diagram of FIG. 36I, if the error message is notfor a valve closure fault, then a decision block (944) determines if theerror was for an ultrasound fault. This error occurs if excessive airhas been detected by the ultrasonic air detector (130). If so, then anerror message is generated at the block (937) and the routine ends. Ifan ultrasound fault has not occurred, then one of numerous otherrecoverable errors is assumed. Such errors may include the plunger motorbeing out of position, or the plunger or valve motor not responding.With such error, control proceeds to a block (945) which repositions themechanism to the "home" position and tests the mechanism, as done at theblock (1032) of FIG. 36L, discussed above. A decision block (946)determines if the repositioning is successful. If not, then controlproceeds to the block (937). If so, then the recovery count isincremented at a block (947) and the routine ends.

The fault recovery routine is operable to respond to an error signalindicating error from which the pump driving mechanism can recovery byrepositioning the pump driving mechanism to a reselect neutral positionprior to continuation of an infusion pumping sequence.

Thus, in accordance with the invention there is illustrated a medicalambulatory infusion pump which accurately and safely administers a widerange of infusion rates.

We claim:
 1. In a peristaltic infusion pump having a housing defining apump chamber cassette, the pump chamber cassette including a pumpchamber assembly having a lumen, the housing further containing a pumpdriving mechanism including at least an inlet and an outlet pinchervalve, means for maintaining the pump chamber cassette in an operativeposition relative to the pump driving mechanism and means for actuatingthe pump driving mechanism pincher valves to constrict the lumen of thepump chamber at spaced points along the pump chamber assembly bycompressing the pump chamber assembly against a platen to propel liquidthrough the pump chamber assembly, an improved pump chamber cassettecomprising:a pump chamber assembly comprising an elastomeric tube havingan inlet valve portion and an outlet valve portion made of a firstmaterial and a tubular chamber portion disposed therebetween, thechamber portion being made of a second material, there being a lumenthrough the inlet and outlet valve portions and the chamber portion, thefirst material having a durometer less than a durometer of the secondmaterial, one of the valve portions and the chamber portion having afootball-shaped cross section; a rigid frame; and means for attachingthe elastomeric tube to the frame, the attaching means maintaining theelastomeric tube between the valve pinchers and the platen with theminor axis of the football-shaped cross-section aligned parallel to thedirection of the movement between the valve pinchers and the platen withthe cassette received in the operative position within a cassettereceptacle.
 2. The improvement pump chamber cassette of claim 1 whereinthe attaching means comprises:clips spaced lengthwise along theelastomeric tube; means bonding the clips to the elastomeric tube; andcooperating means between the clips and the rigid frame for fasteningthe clips to the rigid frame in a spaced relation.
 3. The improvementpump chamber cassette of claim 2 wherein the elastomeric tube is made ofpolyvinylchloride.
 4. The improved pump chamber cassette of claim 1wherein the peristaltic infusion pump pumping mechanism further includesa plunger intermediate the inlet and outlet pincher valves and the inletvalve portion and the outlet valve portion have football-shapedcross-sections and the pump chamber portion has a round cross-section,the inlet valve portion, the pump chamber portion and the outlet valveportion being spaced so that with the pump chamber cassette in theoperative position within the pump chamber cassette receptacle, theinlet valve portions proximate the inlet pincher valve, the chamberportion is proximate the plunger and the outlet valve portion isproximate the outlet pincher valve.
 5. The improved pump chambercassette of claim 1 wherein the first material is polyvinylchloride andthe second material is polyurethane.
 6. The improved pump chambercassette of claim 5 wherein the chamber portion has a football-shapedcross-section.
 7. A pump chamber assembly for use with a medicalinfusion pump, the medical infusion pump having a housing defining apump chamber receptacle, the housing further containing a pump drivingmechanism including an inlet pincher valve, an outlet pincher valve anda plunger intermediate the inlet and outlet pincher valves, means foractuating the pump driving mechanism to propel liquid through the pumpchamber assembly, and means for maintaining the pump chamber assemblywithin the pump chamber receptacle in an operative position relative tothe pump driving mechanism, the pump chamber assembly comprising:anelongate elastomeric tube having a tubular inlet valve portion and atubular outlet valve portion and a tubular chamber portion disposedtherebetween, the inlet and outlet valve portions having a wallthickness greater than the wall thickness of the chamber portion, theinlet valve portion, the outlet valve portion and the chamber portionbeing spaced so that with the pump chamber in an operative positionwithin the pump chamber receptacle the inlet valve portion is proximatethe inlet pincher valve, the chamber portion is proximate the plungerand the outlet valve portion is proximate the outlet pincher valve. 8.The pump chamber assembly of claim 7 wherein the inlet and outlet valveportions are made of a first material and the chamber portion is made ofa second material, the first material having a durometer less than adurometer of the second material.
 9. The pump chamber assembly of claim8 wherein the first material is polyvinylchloride and the secondmaterial is polyurethane.